TRIPOLI, Libya - More than a thousand inmates escaped a prison Saturday in Libya as protesters stormed political party offices across the country, signs of the simmering unrest gripping a nation overrun by militias and awash in weaponry.

It wasn't immediately clear if the jailbreak at al-Kweifiya prison came as part of the demonstrations. Protesters had massed across Libya over the killing of an activist critical of the country's Muslim Brotherhood group.

Inmates started a riot and set fires after security forces opened fire on three detainees who tried to escape the facility outside Benghazi, a security official at the prison said. Gunmen quickly arrived at the prison after news of the riot spread, opening fire with rifles outside in a bid to free their imprisoned relatives, a Benghazi-based security official said.

Those who escaped either face or were convicted of serious charges, the prison official said.

Special forces later arrested 18 of the escapees, while some returned on their own, said Mohammed Hejazi, a government security official in Benghazi. The three inmates wounded in the initial escape attempt were taken to a local hospital, he said.

There was confusion, however, about how many prisoners exactly broke out, with numbers of escapees ranging as high as 1,200.

Meanwhile Saturday, hundreds gathered in the capital Tripoli after dawn prayers, denouncing the Friday shooting death of Abdul-Salam Al-Musmari. They set fire to tires in the street and demanded the dissolution of Islamist parties.

The two incidents highlighted Libya's deteriorating security situation and the challenges the North African country faces as it tries to restore calm nearly two years after the ouster and killing of longtime dictator Moammar Gadhafi.