TRIPOLI, Libya — An explosion believed to have been caused by a bomb ripped through the military intelligence building in Libya's eastern city of Benghazi at dawn Wednesday, causing damage to the structure and nearby homes but no injuries, a security official said.

The blast took place hours after gunmen stormed a jail in Benghazi and freed Islamist militant Salem al-Obeidi, the suspected killer of former rebel chief Abdel-Fattah Younis, according to a second security official.

Younis served as Moammar Gadhafi's interior minister until he joined the anti-regime uprising last year. He was killed in July 2011.

The blast and the raid on the city's jail underline Libya's tenuous security situation nearly a year after Gadhafi's ouster. Former rebels have refused to lay down their arms and operate as the de facto government in many parts of the vast Arab nation.

The two officials spoke on condition of anonymity because they were not authorized to speak to the media.

Benghazi is the birthplace of the Libyan uprising that led to Gadhafi's ouster and served as the rebellion's capital throughout the months of civil war that ended with the dictator's capture and death last October.