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Libyan leader Muammar al-Qaddafi vows to fight to the "last man and woman" to defend his country as forces loyal to him battled government opponents for control of a key oil installation and an airstrip Wednesday on the Mediterranean coast in a counter-offensive against the rebel-held eastern half of the country.

Opponents of Qaddafi repelled an attack by the Libyan leader's forces trying to retake a key coastal oil installation in a topsy-turvy battle in which shells splashed in the Mediterranean and a warplane bombed a beach where rebel fighters were charging over the dunes. At least five people were killed in the fighting.

The assault on the Brega oil port was the first major regime counteroffensive against the opposition-held eastern half of Libya, where the population backed by mutinous army units rose up and drove out Qaddafi's rule over the past two weeks.

"We will fight until the last man and woman. We will defend Libya from the north to the south," Qaddafi said while addressing supporters and foreign media in a conference hall in the capital Tripoli.

"We will not accept an intervention like that of the Italians that lasted decades," he said during a rambling speech, referring to Italy's colonial rule early in the 20th Century. "We will not accept a similar American intervention. This will lead to a bloody war and thousands of Libyans will die if America and NATO enter Libya."

Qaddafi's forces are escalating a counteroffensive, pushing the country closer to an all-out civil war.

Fighting has intensified over the past two weeks after government opponents seized control of the eastern half of the country and several cities and towns in the western half near the capital Tripoli.

Anti-government protesters have garnered broad support from their homegrown opposition movements and fear foreign aid could work against them.

Brega lies at the western edge of the swathe of opposition-controlled territory of eastern Libya. At the nearby rebel-held city of Ajdabiya, pick-up trucks full of anti-Qaddafi fighters carrying automatic weapons, along with a tank, sped out toward the oil port, 40 miles away.

At the same time, Ajdabiya's people geared up to defend the city, fearing the pro-Qaddafi forces would move on them next. At the gates of the city, hundreds of residents took up positions on the road from Brega, armed with Kalashnikovs and hunting rifles, along with a few rocket-propelled grenade launchers. They set up two large rocket launchers and an anti-aircraft gun in the road.

Ahmed Dawas, an opposition fighter at a checkpoint outside Brega, said a large force of pro-Qaddafi fighters in about 50 SUVs descended on Brega shortly after sunrise and swept over the facility, taking the airstrip as warplanes struck nearby targets. But later, he said, anti-regime fighters from Ajdabiya and from Brega's residents flooded in and took back it back.

There was no immediate word on casualties.

Libyan forces have launched repeated airstrikes during the two-week revolt but all of them have been reported to target facilities that store weapons in areas controlled by the rebellion. However, some air forces have said they bailed out because they were ordered to bomb civilians.

A revolutionary council in Libya reportedly debated Tuesday whether to ask the United Nations to execute airstrikes against pro-Qaddafi forces. The council aims to distinguish between help from the U.N. and foreign intervention, which the rebel forces oppose, according to the New York Times.

Diplomats at NATO and the European Union say some countries are already drawing up plans to prevent Qaddafi's air force from carrying out air strikes against the rebels.

NATO has said that any such move would require a clear mandate from the U.N. Security Council. This is unlikely because Russia, which has veto power in the council, has already rejected the idea.

According to diplomats, the plans being considered are modeled on the no-fly zones over the Balkans in the 1990s in case the international community decides to impose an air embargo over Libya.

Witnesses told the AP they saw two warplanes bomb the eastern outskirts of Ajdabiya at 10 a.m. local time.

They also said pro-Qaddafi forces were advancing on the town, some 470 miles east of the capital Tripoli.

"I see two jets bombing now," said one witness who, like the others, spoke on condition of anonymity because he feared reprisals. Another witness said rebel forces were rushing to the western side of Ajdabiya to meet the advancing pro-Qaddafi force.

"We are ready to repel their attack," said the witness.

An exact death toll has been difficult to obtain in the chaos, but a medical committee in the eastern city of Benghazi, where the uprising began on Feb. 15, said at least 228 people had been killed, including 30 unidentified bodies, and 1,932 wounded.

U.N. Secretary General Ban Ki-moon has cited reports that perhaps 1,000 have died in Libya.

One Libyan human rights group says that 6,000 have died since fighting began.

The Obama administration knows the Libyan opposition wants to be seen as “doing this by themselves on behalf of the Libyan people – that there not be outside intervention by an external force,” Secretary of State Hillary Clinton told the House Foreign Affairs Committee Tuesday.

On Tuesday, U.S. Defense Secretary Robert Gates ordered U.S. warships to move closer to the Libyan Coast.

Amphibious assault ships USS Kearsarge and USS Ponce have reached the Mediterranean, a U.S. official told Reuters. The USS Kearsarge is carrying some 42 helicopters on board, two officials said.

Gates said he was sending 400 Marines to the vessels to replace some troops that left recently for Afghanistan.

Gates also said any military action in Libya must be carefully weighed because of broad consequences for the region.

The Associated Press contributed to this report.