An airstrike conducted by NATO planes enforcing the UN-sanctioned no-fly zone over Libya on Friday has killed 13 rebel fighters, Reuters reports.

“Some of Qaddafi’s forces sneaked in among the rebels and fired anti-aircraft guns in the air,” rebel fighter Mustafa Ali Omar told the press. “After that, the NATO forces came and bombed them.”

The deaths, which took place during the chaotic battle between Muammar Qaddafi's forces and rebel-fighters in the oil town of Brega, was termed a "regrettable incident" by rebel-leadership spokesman Hafiz Ghoga.

Despite the deaths on Friday night, rebel leaders called for continued air strikes against Qaddafi's forces, who have dramatically reversed an impetuous rebel advance on the coastal road linking their eastern stronghold with western Libya.

“The military leadership is working on ways to prevent a recurrence,” Ghoga told reporters at the rebel headquarters in the eastern city of Benghazi. 

Another rebel spokesperson, Mustafa Gheriani, told Reuters the leadership still wanted and needed allied air strikes. “You have to look at the big picture. Mistakes will happen. We are trying to get rid of Qaddafi and there will be casualties, although of course it does not make us happy.”

In Brussels, a spokesperson for NATO, which this week assumed command of the military operation, said the alliance was looking into the reports.

Brega Situation Unclear

Qaddafi forces fired rockets on Brega overnight and fighting continued further west around the town’s university early on Saturday, rebels said. But at the eastern gate of the town, dust rose from the road as volunteers known as the “shebab," or youth, streamed away in cars after coming under heavy fire from Qaddafi’s forces.

A contingent of more experienced and better organized rebel units initially held their ground in Brega, but with most journalists forced east, it was unclear whether they had remained inside the town or had pulled back into the desert.

Brega is one of a string of oil towns along the coast that have been taken and retaken by each side after the UN mandated intervention which was intended to protect civilians in Libya.

Rebels have been trying to marshal their rag-tag units into a more disciplined force after a rebel advance along about 200 kilometers of coast west from Brega was repulsed and turned into a rapid retreat this week. By mid-afternoon on Saturday, dozens of volunteer fighters were waiting with their pick-ups at a checkpoint east of Brega.

Volunteer fighter Khalid Salah told the press the rebels were waiting for the arrival of heavy weapons to begin another counterattack. Aircraft could be occasionally overhead.

Qaddafi Not Interested In Ceasefire

On Friday, a rebel leader, speaking after talks with a UN envoy in Benghazi, offered a truce on condition that Qaddafi left Libya and his forces quit cities under government control.

But Qaddafi's government, which has seized the initiative in Libya's civil war, dismissed the ceasefire call.

“They are asking us to withdraw from our own cities," spokesperson Mussa Ibrahim told reporters. "If this is not mad, then I don’t know what this is. We will not leave our cities.”

State-controlled Libyan television said coalition forces bombarded “civilian and military locations” in western Libya late on Friday. It said the strikes were in the towns of Khoms, between the capital Tripoli and Misrata, and Arrujban, in the southwest.