The rebels have launched an offensive early in the morning on three different fronts and battles are intense and violent, say the sources.
Gaddafi opposing forces, which seem better organized and equipped military have launched rockets and shells on the positions taken by those loyal to the regime in Tripoli and forced them to retreat to the center of Brega, the sources said.
Early in the afternoon and while they were still fighting ground, a NATO aircraft bombed positions gadafistas forces, added the sources.
Al Jazeera has broadcast images of distant artillery fire and numerous rebel columns of black smoke, while explaining that Gaddafi's forces have been concentrated mainly in the vicinity of the city's industrial zone.
Aided by air strikes by aircraft of the Allied forces, rebel troops retook control, ten days ago, the city of Brega, as a bridgehead of an offensive that they should allow the collection of Sirte, the town Gaddafi's home.
But gadafistas brigades counterattacked and forced the rebels to retreat to the nearby city of Ajdabiya.