BENGHAZI, Libya (AP) - Foreign mercenaries and Libyan militiamen loyal to Moammar Gadhafi tried to roll back the uprising against his rule that has advanced closer to his stronghold in Tripoli, attacking two nearby cities in battles that killed at least 17 people. But rebels made new gains, seizing a military air base, as Gadhafi blamed Osama bin Laden for the upheaval.
The worst bloodshed was in Zawiya, 30 miles west of the capital Tripoli. An army unit loyal to Gadhafi opened fire with automatic weapons on a mosque where residents - some armed with hunting rifles for protection - have been holding a sit-in to support protesters in the capital, a witness said.
The troops blasted the mosque's minaret with an anti-aircraft gun. A doctor at a field clinic set up at the mosque said he saw the bodies of 10 dead, shot in the head and chest, as well as around 150 wounded. A Libyan news website, Qureyna, put the death toll at 23 and said many of the wounded could not reach hospitals because of shooting by "security forces and mercenaries."
A day earlier, an envoy from Gadhafi had come to the city from Tripoli and warned the protesters: "Either leave or you will see a massacre," the witness said. On Tuesday night, Gadhafi himself called on his supporters to hunt down opponents in their homes.
Zawiya, a key city close to an oil port and refineries, is the nearest population center to Tripoli to fall into the hands of the anti-Gadhafi rebellion that began Feb. 15. Hundreds have died in the unrest.
Most of the eastern half of Libya has already broken away, and diplomats, ministers and even a high-ranking cousin have abandoned Gadhafi, who has ruled Libya for 41 years. He is still believed to be firmly in control only of the capital, some towns around it, the far desert south and parts of Libya's sparsely populated center.
Gadhafi's crackdown has been the harshest by any Arab leader in the wave of protests that has swept the Middle East the past month, toppling the presidents of Libya's neighbors - Egypt and Tunisia. The New York-based Human Rights Watch has put the death toll in Libya at nearly 300, according to a partial count. Italy's Foreign Minister Franco Frattini said estimates of some 1,000 people killed were "credible."
Hours after the attack in Zawiya, Gadhafi called in to state TV and in a rambling speech expressed condolences for the dead but then angrily scolded the city's residents for siding with the uprising.
He blamed the revolt on bin Laden and teenagers hopped up on hallucinogenic pills given to them "in their coffee with milk, like Nescafe."
"Shame on you, people of Zawiya, control your children," he said, addressing residents of the city outside Tripoli where the mosque attack took place. "They are loyal to bin Laden," he said of those involved in the uprising. "What do you have to do with bin Laden, people of Zawiya? They are exploiting young people ... I insist it is bin Laden."
Thousands massed in Zawiya's main Martyrs Square by the Souq Mosque after the attack, shouting for Gadhafi to "leave, leave," the witness said. "People came to send a clear message: We are not afraid of death or your bullets," he said.
In the latest blow to the Libyan leader, a cousin who is one of his closest aides, Ahmed Gadhaf al-Dam, announced that he has defected to Egypt in protest against the regime's bloody crackdown, denouncing what he called "grave violations to human rights and human and international laws."
Gadhaf al-Dam is one of the highest level defections to hit the regime so far, after many ambassadors around the world, the justice minister and the interior minister all sided with the protesters. Gadhaf al-Dam belonged to Gadhafi's inner circle, served as his liaison with Egypt and frequently appeared by his side.
The regime's other attempt to take back lost territory came east of Tripoli. Pro-Gadhafi militiamen - a mix of Libyans and foreign mercenaries - assaulted a small airport outside Libya's third largest city, Misrata, about 120 miles from the capital.
Militiamen with rocket-propelled grenades and mortars barraged a line of government opponents who were guarding the airport, some armed with rifles, said one of the rebels who was involved in the battle.
During the fighting, the airport's defenders seized an anti-aircraft gun used by the militias and turned it against them, he said.
At the same time, officers from an air force school near the airport mutinied and, along with residents, overwhelmed an adjacent military air base where Gadhafi loyalists were holed up, a medical official at the base said. The air force personnel disabled fighter jets at the base to prevent them from being used against the uprising, he said.