EAST OF BREGA, Libya (Reuters) - A NATO-led air strike killed 13 Libyan rebels in a "regrettable incident," a rebel spokesman said on Saturday, in an increasingly chaotic battle with Muammar Gaddafi's forces over the oil town of Brega.
Despite the deaths on Friday night, the rebel leadership called for continued air strikes against Gaddafi's forces, who have reversed a rebel advance on the coastal road linking their eastern stronghold with western Libya.
Hundreds of mostly young, inexperienced volunteers were later seen fleeing east from Brega toward the town ofAjdabiyah after coming under heavy mortar and machinegun fire.
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.
A Reuters correspondent visiting the scene of the air strike saw at least four burned-out vehicles including an ambulance by the side of the road near the eastern entrance to the town.
Men prayed at freshly dug graves covered by the rebel red, black and green flag nearby.
"Some of Gaddafi's forces sneaked in among the rebels and fired anti-aircraft guns in the air," said rebel fighter Mustafa Ali Omar. "After that the NATO forces came and bombed them."
The strike killed 13 rebels and wounded seven, rebel leadership spokesman Hafiz Ghoga said, calling it a "regrettable incident."
"The military leadership is working on ways to prevent a recurrence," Ghoga told reporters at the rebel headquarters in the eastern city of Benghazi. Rebels at the scene said the bombing happened around 10 p.m. local time on Friday.
Another rebel spokesman, 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 Gaddafi and there will be casualties, although of course it does not make us happy."
In Brussels, a spokeswoman for NATO, which this week assumed command of the military operation launched on March 19, said the alliance was looking into the reports.
Gaddafi 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 Gaddafi's forces.
The volunteers have frequently fled under fire, raising questions about whether the rebels can make any headway against Gaddafi's better-equipped and better-trained forces without greater Western military involvement.
REBELS FEAR INFILTRATION BY GADDAFI LOYALISTS
Brega is one of a string of oil towns along the coast that have been taken and retaken by each side after the U.N. 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 km (125 miles) 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 said the rebels were waiting for the arrival of heavy weapons to begin another counter-attack. Aircraft could be heard occasionally overhead.
The stalled rebel campaign has left rebel-held areas in western Libya, notably the city of Misrata, stranded and facing intense attacks from Gaddafi's forces.
One Benghazi-based rebel said food supplies were acutely low in Misrata due to the siege. The rebel, called Sami, said he was in regular contact with a Misrata resident who had told him one person died and six were injured in clashes on Saturday.
"There are severe food shortages and we call on humanitarian organizations to help," said Sami. "The city has been under siege for a month and a half. The main shortages are fruit and vegetables because those come from the south and the southern entrance to the city is controlled by Gaddafi's men."
Contacted by Reuters, Sami reported sporadic clashed on Saturday after heavy fighting on Friday, when fire from a tank belonging to pro-Gaddafi forces hit a dairy factory.
"They are trying to starve and kill people inside the city by all means," said a British-based doctor who had spoken to his friends in Misrata on Saturday.
On Friday, a rebel leader, speaking after talks with a U.N. envoy in Benghazi, offered a truce on condition that Gaddafi left Libya and his forces quit cities under government control.
The Libyan government dismissed the ceasefire call.
"They are asking us to withdraw from our own cities .... If this is not mad then I don't know what this is. We will not leave our cities," spokesman Mussa Ibrahim told reporters.'
State-controlled Libyan television also said that 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.
Showing footage of two men receiving medical treatment while lying in hospital beds, it said, "This is the result of attacks by crusader aggressors in Khoms."
One of the men was shown lying in bed with a bandaged right foot. Blood could be seen on the bandage. The other man was shown having his chest stitched up by a female medic.
A resident in Khoms, contacted by telephone, said he had heard the bombing on Friday. "It was from the area of the naval base," he said. "Today it is quiet."
(Additional reporting by Angus MacSwan in Benghazi, Tom Pfeiffer in Cairo, Maria Golovnina in Tripoli; Joseph Nasr in Berlin, writing by Myra MacDonald/David Stamp; editing by Matthew Jones)