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Increasingly violent clashes in Libya between armed anti-government rebels and forces loyal to Muammar al-Qaddafi threaten to escalate into a civil war, as the two sides battle for control of towns near the capital in the 15th day of fighting.

The intensified combat comes as a revolutionary council in Libya reportedly debates 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.

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

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.

Despite rebels’ efforts to ward off foreign aid, the international community stepped up moves Tuesday to isolate Qaddafi.

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U.S. Defense Secretary Robert Gates said he ordered two ships into the Mediterranean, including the amphibious assault ship USS Kearsarge, and he is sending 400 Marines to the vessel to replace some troops that left recently for Afghanistan.

With fears high that Qaddafi could wage airstrikes against his own people, the European Union and the United States have raised the possibility of a no-fly zone over Libya -- a tactic used successfully in northern Iraq and Bosnia.

But Russian Foreign Minister Sergey Lavrov called the idea "superfluous" and said world powers must instead focus on fully using the sanctions the U.N. Security Council approved over the weekend. Russia is a veto-wielding member of the Security Council.

Susan Rice, the U.S. ambassador to the United Nations, meanwhile, urged Qaddafi to consider exile, saying she's worried the African nation could plummet into a "humanitarian disaster."

"It's important that he get off the stage," Rice said told CBS on "The Early Show."

Qaddafi's son, Seif al-Islam, warned Western forces not to take military action against Libya and said the country is prepared to defend itself against foreign intervention.

"If they attack us, we are ready," he told Sky News, adding that the Qaddafis are ready to implement reforms.

Facing an unprecedented challenge to his 41-year rule, Qaddafi's regime has launched the bloodiest crackdown in a wave of uprising against authoritarian rulers in the Middle East. Qaddafi has already lost control of the eastern half of the country but still holds Tripoli and other nearby cities.

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.

Qaddafi's regime has retaken at least two towns and threatened a third, while rebels repulsed attacks on three other key areas -- Misrata to the east, Zawiya to the west, and the mountain town of Zintan to the south of the capital.

One of those retaken was the strategic mountain town of Gharyan, the largest in the Nafusa Mountains, which overlooks Tripoli, a resident said, speaking on condition of anonymity for fear of government retaliation. The town fell after dark Friday in a surprise attack, and the government troops detained officers who defected to the rebels and drew up lists of wanted protesters and started searching for them, the resident added.

Qaddafi supporters also have said they were in control of the city of Sabratha, west of Tripoli, which has seemed to go back and forth between the two camps in the past week.

But witnesses in Zawiya, 30 miles west of the capital, said rebels shouted "Allahu akbar (God is great) for our victory," and carried an air force colonel who had just defected after six hours of overnight gunbattles failed to dislodge anti-Qaddafi forces who control the city.

"We were worried about air raids but that did not happen," said one resident, who spoke on condition of anonymity for fear of reprisals.

The Zawiya rebels have tanks, machine guns and anti-aircraft guns. They beat back pro-Qaddafi troops, armed with the same weapons, who attacked from six directions. There was no word on casualties.

In Misrata, 125 miles east of Tripoli, pro-Qaddafi troops who control part of an air base on the city's outskirts tried to advance Monday. But they were repulsed by opposition forces, who included residents with automatic weapons and defected army units allied with them, one of the opposition fighters said.

No casualties were reported and the fighter claimed that his side had captured eight soldiers, including a senior officer.

The opposition controls most of the air base, and the fighter said dozens of anti-Qaddafi gunmen have arrived from farther east in recent days as reinforcements.

One sergeant in the Libyan army who is of Tuareg ethnicity and is fighting on Qaddafi's side said the military is divided.

"Us foreigners, we don't have much choice. We have to support Gaddafi," he said in a telephone interview with The Associated Press in Mali. "It because of him we are here."

He added that everyone who supports Qaddafi has not been watching any foreign news.

"There is nothing that's going to convince Gaddafi to quit," the soldier said. "The only way Gaddafi is going to go is if someone puts a bullet in his head, and I can't imagine that. The soldiers who are close to him would never let it happen."

The Associated Press contributed to this report.