Paramilitary groups and other forces loyal to Libyan leader Moammar Gadhafi battled for control over a major oil refinery and a massive weapons depot Wednesday in a counter-offensive against the rebel-held eastern half of the country.

The fighting was centered on the oil facilities at Brega, which lies at the western edge of the opposition-controlled territory in the east. Witnesses told The Associated Press on Wednesday morning that it had been retaken by a large convoy of pro-Gadhafi forces. But hours later, people on the outskirts of Brega said fighting resumed.

They said some of the regime’s forces were surrounded by rebels. The sound of screaming warplanes and the crackle of heavy gunfire could be heard as the witnesses spoke by phone. Opposition fighters at checkpoints outside Brega said the opposition had retaken the oil facilities and an airstrip.

Ahmed Dawas, an opposition fighter at a checkpoint outside Brega, said a large force of pro-Gadhafi 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.

Rebel fighters carrying automatic weapons, along with a tank, sped out of the nearby city of Ajdabiya in pickup trucks toward the oil port 40 miles away to join the fight.

At the same time, Ajdabiya’s people geared up to defend their city from attacks by the regime. NPR’s Lourdes Garcia-Navarro, reported from the opposition-held city of Benghazi, said there have been several bombing attempts on Ajdabiya, the site of a key weapons depot.

“The weapons depot there is vast. It has about 35 warehouses filled with all sorts of munitions, including surface-to-air missiles, rocket-propelled grenade launchers and other arms. And so it is a very strategically important place for the rebel army and clearly also for pro-Gadhafi forces.”

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.

Scores of armed young men also streamed out of Benghazi, which is seen as the capital of “free Libya,” to reinforce pro-democracy forces in Brega and Ajdabiya, Garcia-Navarro said.

“They say they are willing to die to maintain their hold of eastern Libya,” she said. “And not only their hold of eastern Libya. They say that once they have defended this place, they will push out and try and overthrow Moammar Gadhafi once and for all.”

In the capital, Gadhafi repeated claims that al-Qaida is behind the uprising, telling a gathering of supporters Wednesday that a “sleeper cell” launched the protests.

Some opposition members told the AP that they believe Gadhafi was pulling up reinforcements from bases deep in the deserts of southwestern Libya, flying them to the fronts on the coast. Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.