Hundreds of rebels retreated east of Brega under artillery fire earlier in the day before regrouping and firing back with their own rockets. Black smoke rose from the west side of the town, and some rebels suggested that better-trained fighters, possibly defected army troops, were still battling Gaddafi's soldiers inside.
Rebels had managed to advance to a walled university campus near the town's western edge where fighting has swirled since opposition troops first reached the area one month ago. But despite air strikes on Gaddafi's forces that rebels reported hearing on Saturday night, they seemed unable to move further.
"If you compare where we are today to where we were a few weeks ago, then we are in the exact same position," said Al Jazeera's Hoda Abdel-Hamid, reporting from Ajdabiya.
The rebels seem able to advance only when Gaddafi's forces pull out, she said, though the opposition claims it is still trying to bring order to its nascent army.