TRIPOLI - Libyan security forces started a large-scale search Monday in the capital Tripoli after a mass prison break, a source said.

Some 120 prisoners are on the run after they escaped from the Jadeida prison in Tripoli Monday afternoon, the source told Xinhua on condition of anonymity.

The security forces are on high alert across the city and are conducting a large-scale search around the prison, the source said.

The source added the prison break occurred due to "weak security measures" of the jail, one of the largest in the country.

Human rights groups have reported human rights abuses in the prison.