BENGHAZI, Libya — A powerful blast caused serious damage to a foreign ministry building in the eastern Libyan city of Benghazi on Wednesday, witnesses said.

The explosion comes on the first anniversary of an attack by militants on the United States consulate in Benghazi, which killed four Americans, including the ambassador.

It was not immediately known if the blast, which the witnesses said appeared to have been caused by a car bomb, had resulted in casualties.

An AFP photographer said a large section of the foreign ministry building had been destroyed and parts of the nearby local headquarters of the central bank seriously damaged.

Benghazi, cradle of the 2011 revolt that toppled and killed dictator Moammar Gadhafi, has been hit by a wave of deadly attacks in recent months targeting security force officers and members of the judiciary, many of whom served the previous regime.

Attacks have also targeted diplomats and western interests.

Much of the violence, including the killing of the U.S. ambassador last year, has been attributed to radical Islamists who are deeply rooted in the region.