A Nato airstrike on a military tank near Libya's eastern oil town Brega on Thursday killed two rebels and wounded 10, witnesses and AFP correspondents said.
"It was the planes of Nato. They fired twice at our tank and blew up the tank's position," said rebel fighter Ali Sahli, 41.
An AFP reporter at a hospital in the nearby town of Ajdabiya, citing medical officials, said two rebels had died and around 10 were wounded in the attack.
Chaotic scenes were witnessed at a rebel checkpoint on the edge of Ajdabiya, about 80 kilometres (50 miles) from Brega, with ambulances racing through heading for the hospital followed by a convoy of rebel military vehicles.
Civilians were ordered away from the checkpoint.
Nato warplanes have been targeting Muammar Gaddafi's forces around Brega, where rebels have been halted in their bid to advance on the capital Tripoli and oust the Libyan strongman.
But rebels have accused the alliance of failing in their mission to protect civilians while a chief rebel spokesman said coalition warplanes had killed 13 people, four of them civilians, in an air raid near Brega on April 1.