NEAR BREGA, Libya - Libyan rebels skirmished with government forces around the strategic oil town of Brega on Sunday, making incremental gains backed by international air strikes in the see-saw desert battle for the country.

In contrast to the rapid territorial gains and losses that have characterized the fighting over the past few weeks, the conflict has stabilized recently around the oil facilities of Brega, as better-trained rebel soldiers joined the fight and airstrikes blunted the government advantages in weapons and training.

"There have been skirmishes in Brega," confirmed Rabia al-Ahwat, a rebel fighter. He said there had been heavy airstrikes against government forces. Those strikes have been key in halting the previously unstoppable government advances.

One of those airstrikes went awry late on Friday however, and mistakenly killed 13 rebel fighters. Forces loyal to Gadhafi shelled the besieged western town of Misrata on Sunday where hundreds were reported killed.

Ramadan, a British-based doctor who said he arrived in Misrata on Friday on a humanitarian mission, had no figure for the death toll since fighting began six weeks ago.

"But every week between 100 or 140 people are reported killed - multiply this by six and our estimates are 600 to 1,000 deaths since the fighting started," he said.

After weeks of shelling and encirclement, Gadhafi's forces appear to be gradually loosening the rebels' hold on Misrata. Rebels say they still control the city centre and the port, but that government troops have pushed into the centre.

As well as laying siege to Misrata, Gadhafi's troops have reversed a rebel advance in the east and are mopping up resistance in the mountainous area southwest of Tripoli.

"We are reorganizing our ranks. We have formed our first brigade. It is entirely formed from ex-military defectors and people who've come back from retirement," former Air Force Major Jalid al-Libie said in Benghazi.

The US Obama administration is hoping that if Gadhafi's government doesn't implode soon, a relentless campaign of airstrikes on his tanks, air defenses and most trusted army units will at least weaken his ability to survive a renewed uprising by a disjointed opposition.

Starting Sunday, US combat aircraft ceased strike missions in Libya, but NATO's on-scene commander can request US strikes in the days ahead, in which case they may have to be approved in Washington.

On the political front, the US and its allies are hoping that the defection to Britain on Wednesday by Libya's Foreign Minister Moussa Koussa is a sign of things to come.

AP-Reuters