AJDABIYAH (Agencies) - A Nato airstrike hit a Libyan rebel position near the oil town of Brega on Thursday, killing at least 13 people including rebel fighters, doctors in Ajdabiya said. A doctor from a rebel ambulance that had been at the front said they were also hit shortly after the airstrike by a rocket attack from forces supporting Muammar Gaddafi. One medical worker was killed and a doctor was severely wounded, he told Reuters. A Reuters reporter saw bloodstained stretchers being brought out of the hospital in Ajdabiyah, where those wounded in the air and rocket attacks were being treated. Medical staff could be seen fighting to save the life of the wounded doctor. One rebel commander told the BBC he saw at least four missiles land among rebel fighters. Many people have been killed and many more have been injured, he said. Civilians are reported to be fleeing Ajdabiya in their thousands, according to the latest wire reports, after rumours spread that Gaddafi forces were preparing to attack the city. It was a Nato airstrike on us. We were near our vehicles near Brega, wounded fighter Younes Jumaa said from his stretcher at the hospital. It was the second time in less than a week that rebels blamed Nato for bombing their comrades by mistake. Thirteen died in an airstrike not far from the same spot on Saturday. Nurse Mohamed Ali said at least five people died in Thursdays attack. Medical workers carried uniforms soaked in blood from one of hospital rooms. Some rebel fighters were weeping on their knees in the corridor. We were standing by our tanks and Nato fired two rockets at us, said one, Salem Mislat. Nato are liars. They are siding with Gaddafi. Doctor Othman al-Faidory told Reuters ambulances near the rebel position came under government rocket attack shortly after the airstrike. I heard airplanes overhead then suddenly there were strikes on the area and then there were rocket attacks from the direction of Gaddafi forces, he said. Later a Reuters reporter heard blasts from the west of Ajdabiyah, gateway to the insurgent stronghold of Benghazi, and a rebel fighter said Gaddafis forces were hitting the western boundary with rockets. Rebel fighters could be seen pulling back from the western entrance to the town, where they have a checkpoint. Meanwhile, Nato denied bombing Libyas biggest oil field after accusations from Gaddafis regime, saying fires at the Al-Sarir field were more likely to be linked to skirmishes in the region. The accusation by Colonel Gaddafi that Nato was responsible for fires in the Sarir Oil Fields is false, Nato said in a statement from its base in Naples which is overseeing military operations in Libya. In a separate incident, seven civilians died and 25 were hurt in a coalition airstrike on a pro-Gaddafi convoy near Brega.