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Israeli warplanes struck the highway linking Beirut to the Syrian capital of Damascus early Friday, closing the country's main artery and further isolating Lebanon from the outside world, Lebanese security officials said.

Fighter jets attacked a highway section high in the mountains of central Lebanon, in Mdeirej. But the targeted area was an old road extension, and the bridge on the nearby main highway remained intact, the officials said.

Another airstrike apparently targeted the main bridge's exit. Authorities turned back motorists, who will have to take long detours through other winding mountain roads.

Because of the darkness, it was not immediately clear the extent of damage on the main highway. Authorities said they were turning back motorists as a precautionary measure.

The Israeli military has confirmed it attacked the highway.

The highway, which climbs up from Beirut, winds through the mountains before descending into the Bekaa Valley and into Syria, is one of Lebanon's only links with the outside world since Israeli forces imposed a sea, air and land blockade of Lebanon on Thursday.

Also on Thursday, Israel blasted the runways and fuel tanks of Beirut's only international airport for a second time, Lebanese security officials said, while Israel's third-largest city Haifa was hit by two Hezbollah long-range missiles in what officials are now calling a full-fledged war.

A helicopter gunship raked the fuel depots with machine gunfire, while three others fired air-to-surface missiles, the officials added, and TV news video showed flames shooting up from the airport.

Israeli planes also dropped leaflets on Hezbollah's stronghold in Beirut's southern suburb near the airport, where its main leaders are based, calling on residents to avoid areas where Hezbollah operates.

"For your own safety and out of our wish to avoid harming the civilians who are not involved, you should refrain from being present in areas where Hezbollah exists and operates," said the leaflets signed the State of Israel.

Photo Essay: Violence Ignites Mideast

The strike on Haifa is the deepest into Israel so far in what an Israeli official called a "major, major escalation" in the ongoing battle between Lebanon and Israel.

Hezbollah guerillas had threatened such a strike on this city, deep within Israel's border, if Israel targeted Beirut or its southern suburbs, but the group denied responsibility for the Thursday attack. No injuries were immediately reported.

The mid-evening attacks are the latest in an escalating tension that Daniel Ayalon, Israel's ambassador to the United States, is referring to as a "war."

"Israel's objective is to win this war," he said Thursday at the National Press Club in Washington.

President Bush defended Israel's attacks in Lebanon but worried they could weaken or topple the fragile government in Beirut.

"Israel has a right to defend herself," Bush said at a news conference in Germany with Chancellor Angela Merkel. "Every nation must defend herself against terrorist attacks and the killing of innocent life."

Earlier Thursday rockets fired in the northern Israeli town of Nahariya hit a group of journalists, injuring at least one person. An Associated Press photographer was standing with the group when the rocket hit, but was not injured.

Israeli warplanes attacked a Lebanese Rayak army air base near the Syrian border in eastern Bekaa Valley, the first strike on the Lebanese army in Israel's fight with Hezbollah guerrillas that started after Hezbollah took two Israeli solders captive in a bid to free Lebanese prisoners.

Caught in the middle of the fight, the Lebanese government asked the U.N. Security Council to demand a cease-fire by the two sides. Two days of Israeli bombings killed 47 Lebanese and wounded 103, Health Minister Mohammed Jawad Khalife said. Besides the Israeli civilian, eight Israeli soldiers have also been killed — the highest death toll for the army in four years.

Hezbollah guerrillas, who are backed by Iran, seized the soldiers Wednesday in a cross-border raid. Israel has since attacked Lebanon by air and sea and has sent in troops to look for the captured soldiers.

Israel's foreign ministry said Thursday that Lebanese guerillas holding the two soldiers captive are trying to transfer them to Iran. Foreign Ministry spokesman Mark Regev did not disclose the source of his information.

Iran denied the suggestions, saying Jerusalem was "talking absurdities," Reuters reported.

"I strongly deny such reports," Foreign Ministry spokesman Hamid Reza Asefi said. "Because of its desperation and increasing isolation in the world and because of the tension and crisis created inside Israel, it is now talking absurdities."

They were two of dozens of retaliatory attacks by Hezbollah guerrillas on northern Israel in the heaviest cross-border fighting in years, including a rocket attack on the border town of Safed, wounding six people and killing one, witnesses and medics said. It was the first attack on the town since the 1990s. Rockets also hit the town of Carmiel, also in northern Israel. Earlier, a rocket killed a second Israeli woman in the border town of Nahariya.

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Israeli officials have been warning for several years that Hezbollah had rockets that could strike Haifa, 18 miles south of the Lebanon-Israel border; however, Thursday's announcement was the first time Hezbollah — which says it has more than 10,000 Katyusha rockets — confirmed having rockets of such long range.

"The Islamic resistance warns against targeting civilians and the infrastructure," according to a statement read on Hezbollah TV.

Hezbollah said it would "quickly rocket the city of Haifa and nearby areas if the southern suburbs and the city of Beirut are subjected to any direct Israeli aggression."

Earlier Thursday, senior Israeli military officials said Israel warned the Lebanese government that it plans to strike offices and homes of Hezbollah leaders in the southern suburbs of Beirut in their bombing campaign in Lebanon that began Wednesday, after Hezbollah captured two Israeli soldiers.

Israel has hit hundreds of targets in Lebanon, a top Israeli general said.

Maj. Gen. Udi Adam, the chief of Israel's northern command, said Israel was targeting infrastructure in Lebanon that held rockets and other arsenals belong to Hezbollah.

"I imagine over time that we will be able to rid ourselves of this threat entirely," he said. He also said the army was not ruling out sending ground troops into Lebanon.

Israel's army chief, Brig. Gen. Dan Halutz, said Thursday no targets in Lebanon are immune, including the capital, Beirut, if the Lebanese government fails to rein in Hezbollah guerrillas. Israeli security officials also warned Lebanon that Israel would strike the Beirut-Damascus highway, the main land link between Lebanon and the outside world.

Israeli forces intensified their attacks in Lebanon, imposing a naval blockade on the country (Full story) and pounding its only international airport and the Hezbollah TV station during Israel's heaviest air campaign against Lebanon in 24 years.

Tensions sharpened after Hezbollah snatched the two Israeli soldiers, with Israel seeking to end once and for all Hezbollah's presence on the border and the guerrillas insisting to trade the captured soldiers for Arab prisoners.

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In the middle is Lebanon, which Israel holds responsible. The Lebanese government insisted it had no knowledge of the move and did not condone it.

Hezbollah fighters operate with almost total autonomy in southern Lebanon, and the government has no control over their actions. But the government has long resisted international pressure to disarm the group — and two Hezbollah ministers are members of the Lebanese Cabinet. Any attempt to disarm the group by force could lead to sectarian conflict.

The Israeli warnings of more to come caused panic in Beirut, with traffic in the streets thin as people stuck to their homes and stayed away from their jobs. Others packed supermarkets to stock up on goods and long lines formed at gas stations, with many quickly running out of fuel.

Western countries, Russia and the United Nations called for restraint and demanded the soldiers' release. Arab and Lebanese TV stations ran urgent alerts and beamed pictures across the Arab world. One station showed a man holding the head and torso of a baby killed in Israeli attacks.

CountryWatch: Lebanon

Eight Israeli soldiers have been killed in the violence so far, including three who died in Hezbollah's initial raid Wednesday to snatch the two soldiers.

Israeli Defense Minister Amir Peretz said his forces would not allow Hezbollah guerrillas to occupy positions along the southern Lebanese border.

"If the government of Lebanon fails to deploy its forces, as is expected of a sovereign government, we shall not allow Hezbollah forces to remain any further on the borders of the state of Israel," Peretz said.

Air force Maj. Gen. Amir Eshel said the campaign was likely Israel's largest ever in Lebanon "if you measure it in number of targets hit in one night, the complexity of the strikes."

The last major air, ground and sea offensive against Lebanon was in 1996 when about 150 Lebanese civilians were killed.

Travelers to and from Beirut were stranded all over the region and beyond after Israel hit the Beirut airport after dawn on Thursday. Among them was Foreign Minister Fawzi Salloukh, who was returning from a visit to Armenia and — like many — was forced to make his way home through Syria.

Later Thursday, an Israeli missile hit the building housing the main studios of Hezbollah's Al-Manar TV in the south Beirut suburb of Haret Hreik, the channel's press officer Ibrahim Farhat told The Associated Press.

The station continued to broadcast, reporting that an Israeli rocket had hit a "minor transmission unit." One person was hurt in the strike, station manager Abdullah Kassir told Voice of Lebanon radio.

Other strikes hit bridges and roads in the south and deep into eastern Lebanon, striking a civic center attached to a Shiite Muslim mosque near the town of Baalbek, as well as a transmission antenna for Al-Manar, witnesses reported. The group's broadcasts stopped in the area.

Among the Lebanese dead in the strikes were a family of 10 and another family of seven, killed in their homes in the village of Dweir near Nabatiyeh, Lebanese officials said. A Lebanese soldier and a Hezbollah fighter have also been killed.

Meanwhile, helicopter gunships and jet fighters scoured southern Lebanon for guerrillas launching rockets into northern Israel.

Hezbollah fired volleys of rockets at Israeli towns, saying it was using a rocket called "Thunder 1" for the first time. The missile appeared to be more advanced than the inaccurate Katyusha, which has been the standard Hezbollah rocket for years.

Hezbollah has declared it has more than 10,000 rockets and has in the past struck northern Israeli communities in retaliation for attacks against Lebanese civilians.

FOX News' Mike Tobin, David Lee Miller, James Rosen and Cassie Carothers and the Associated Press contributed to this report.