A fire ravaged a depot containing electoral material in the eastern Libyan city of Ajdabiya, an official of the national electoral commission said on Thursday.

"The fire happened before sunrise. All the material, including ballot boxes and ballots, was destroyed," said the official, adding that the cause of the fire was unknown.

A coalition air raid late on Friday killed 13 people, four of them civilians, some 15 kilometers (10 miles) east of the battleground Libyan oil town of Brega, a rebel civilian official told Agence France Presse.

The four civilians comprised an ambulance driver and three medical students from the second city of Benghazi, who were part of a rebel convoy of five or six vehicles, said Issa Khamis, liaison officer for the rebels' transitional government in the town of Ajdabiya, east of Brega.

Libyan rebels seized control of the strategic oil town of Ajdabiya on Saturday, marking their first significant victory over Colonel Moammar Gadhafi's forces since the start of the Western air strikes a week ago.

The rebels, backed by a barrage of Western bombardment, powered into the town, leaving a trail of destroyed tanks and military vehicles along the road, Agence France Presse correspondents at the scene reported.

Libyan forces carried out an air strike on the edge of the rebel-held town of Ajdabiya Friday, as opponents of veteran leader Moammar Gadhafi called for fresh protests in the capital Tripoli.

U.S. President Barack Obama said all options were on the table for driving Gadhafi out of power as the strongman's son said air strikes on rebel-held positions were scare tactics rather than to inflict serious damage.