Israeli warplanes blasted a Palestinian guerrilla base late Wednesday on the outskirts of Beirut, trying to pin down Hezbollah fighters who earlier in the day crossed the border and killed eight Israeli soldiers, kidnapping two others.
Hezbollah's raid opened a second front for the Israeli army, which now is fighting Islamic militants in both Lebanon and the Gaza Strip, where it continues to hunt for a third kidnapped soldier taken two weeks ago by Hamas-linked militants.
Israeli Prime Minister Ehud Olmert called the Hezbollah raid an "act of war" by Lebanon, and threatened "very, very, very painful" retaliation. The Israeli cabinet, meeting Wednesday night, drew up plans to carry out more military action and call up thousands of reservists.
The Arab League, meanwhile, reportedly was meeting in secret to decide its next move.
"We are concerned about an escalation," an Arab League official told Reuters. "There's a bad humanitarian situation in Gaza, and we don't want that spilling over into Lebanon."
Residents of northern Israeli towns took cover in underground bomb shelters as Hezbollah, an anti-Israel guerrilla group that essentially runs southern Lebanon, launched rockets across the border throughout the day.
Two Lebanese civilians and a Hezbollah fighter also were killed in the border violence. Still, jubilant Hezbollah supporters and Palestinians living in Lebanon fired guns in the air and set off firecrackers at the news of the Israeli soldiers' capture.
Hezbollah leader Sheik Hassan Nasrallah said he would only free the soldiers in a prisoner swap, adding that he was open to a package deal that would include the release of the soldier held captive in Gaza.
"The capture of the two soldiers could provide a solution to the Gaza crisis ... Now that one (held in Gaza) plus two (held by Hezbollah) makes three," Nasrallah told a news conference in his stronghold of south Beirut.
Israeli Maj. Gen. Udi Adam, head of the northern command, said Israel had "no advance" warning of the Hezbollah attack. He also said Israel has "no intention at the moment of involving Syria," which has great influence over Hezbollah.
"We think at the moment the debate is between us and the government of Lebanon," Adam said.
Army Chief of Staff Lt. Gen. Dan Halutz warned the Lebanese government that the military will target infrastructure and "turn back the clock in Lebanon by 20 years" unless the soldiers were freed. In the past, Israel hit power stations feeding electricity the Lebanese capital, where one third of the country's 3.5 million residents live.
Israel also escalated its Gaza assault early Thursday when an Israeli warplane bombed the Palestinian Foreign Ministry building in Gaza City, collapsing part of the structure and causing widespread damage in the area.
The third and fourth floors of the building were destroyed in the huge blast that shook the city and damaged houses and vehicles for a wide area around it. At least 13 people were injured, all in nearby houses. It was not known if anyone was in the ministry building when the plane struck after 1:30 a.m. (2330 GMT Wednesday).
It was Israel's second use of a huge bomb in Gaza in as many days in its two-week offensive. Warplanes earlier dropped a quarter-ton bomb on a home before dawn in an attempt to assassinate top Hamas fugitives. The head of Hamas' military wing, Mohammed Deif, was wounded but escaped, Israel said. The blast also killed nine members of a Palestinian family — including a 4-year-old boy.
U.S. Assistant Secretary of State David Welch, on a visit to Cairo, Egypt, said the capture of the two Israeli soldiers by Hezbollah was "a very dangerous escalation" that "puts at risk all the effort thats being put forth by many to find a solution to the current situation."
U.N. Secretary General Kofi Annan called for the immediate release of Israeli soldiers and condemned Israel's immediate retaliation. "We would not want to see an expansion, an escalation of conflict in the region," he said in Rome.
The top U.N. official in Lebanon, Geir Pedersen, met with Lebanon's prime minister and said Hezbollah had crossed the border, known as the Blue Line, into northern Israel.
"Hezbollah's action escalates the already tense situation along the Blue Line and is an act of very dangerous proportions," he said in a statement.
The Israeli army said three soldiers were killed in the initial raid, and four others were killed when their tank hit a land mine in southern Lebanon. An eighth soldier was killed as an Israeli force tried to get to the tank, which was part of a ground invasion aimed at rescuing the captured soldiers.
Olmert said he held the Lebanese government responsible for the two soldiers' safety, vowing that the Israeli response "will be restrained, but very, very, very painful."
By the afternoon, seven hours after the Hezbollah raid, Israeli military aircraft were striking large areas of southern Lebanon — targeting bridges, roads and Hezbollah positions in areas as deep as halfway between the Israeli border and the Lebanese capital, Beirut, Lebanese security officials said.
Some bridges were hit more than once to ensure destruction.
An Israeli army statement said the air force attacked more than 30 targets in south Lebanon to prevent the transfer of the kidnapped soldiers.
Several dozen ground troops entered southwestern Lebanon across the border where the soldiers were snatched, apparently only going a short distance in, witnesses said.
Later in the day, a Hezbollah fighter tried to infiltrate an Israeli position on the border and was killed, the Israeli military said. A number of rockets were also fired into northern Israel, prompting residents to flee into shelters.
The Hezbollah raid that captured the soldiers came in the morning. Fighters first fired a volley of Katyusha rockets, then attacked Israeli soldiers on patrol and abducted two, causing other casualties, said Capt. Jacob Dallal, an Israel army spokesman.
Hezbollah's military arm said in a statement that its fighters captured two Israeli soldiers "on the border with occupied Palestine, fulfilling the promise to liberate its prisoners" held by Israel. It said the prisoners were moved to "a safe area."
A top Hamas leader said his movement did not coordinate with Hezbollah over the capture of the soldiers, but said it was "natural" for the two groups to work together in their demands for prisoner swaps with Israel.
"It is early to talk about details of the exchange, but no doubt the operation carried out by Hezbollah today will strengthen our demands to exchange the captives," Osama Hamdan, Hamas' spokesman in Lebanon, told The Associated Press.
Hamas-linked militants have demanded the release of at least some of the estimated 9,000 prisoners held by Israel in exchange for Shalit's freedom.
Hezbollah, which has been clashing with Israel for more than two decades, has repeatedly expressed its intent to kidnap Israeli soldiers to trade for Arab prisoners.
Israel occupied a small strip of southern Lebanon for 18 years before withdrawing in 2000 after high casualties on both sides raised public complaints in Israel. But Israel and Hezbollah still clash over a small sliver of border territory. Chebaa Farms, claimed by Lebanon.
Hezbollah fighters have controlled the Lebanese side of the border with Israel since Israeli forces pulled out. Lebanon is under U.N. and American pressure to disarm the Shiite guerrilla group and move its own military into the south, but the government has refused to do so, calling them a legitimate resistance group.
Israel has carried out several prisoner swaps with Hezbollah in the past to obtain freedom for captures Israelis. These include a January 2004 swap in which an Israeli civilian and the bodies of three Israeli soldiers were exchanged for 436 Arab prisoners and the bodies of 59 Lebanese fighters. In 1985, three Israeli soldiers captured in Lebanon in 1982 were traded for 1,150 Lebanese and Palestinian prisoners.
The Associated Press contributed to this report.