NATO is investigating a report that seven civilians were killed in an airstrike targeting a government convoy.
Twenty five others were reportedly wounded.
Dr Suleiman Refardi told the BBC that the raid on Wednesday happened in the village of Zawia el Argobe, 15km from Brega.
He said there was a direct hit on an ammunition truck and trailer and the resulting explosion destroyed two nearby homes. Other vehicles in the convoy included tanks and artillery.
Air strikes against forces loyal to Colonel Muammar Gaddafi began on 19 March to enforce a 'no-fly' zone declared by the UN. French aircraft were involved.
The Libyan government has rejected a conditional ceasefire offer made by the rebels, saying government forces will not withdraw from towns they control.
A ceasefire was proposed on Friday on the condition that government forces stopped their assault on settlements in the country's east.
But a government spokesperson said the rebels were not offering peace and were making impossible demands.