A powerful car bomb exploded Wednesday near a building used by Libya’s Foreign Ministry in the heart of the eastern coastal city of Benghazi, exactly one year after the Sept. 11 attack there that killed the U.S. ambassador and three other Americans.

The early-morning blast, also on the 12th anniversary of the Sept. 11, 2001, terrorist attacks in the United States, caused no serious casualties, al though several passersby were slightly wounded, authorities said.

No group immediately claimed responsibility. However, the bombing targeted a building that once housed the U.S. Consulate during the rule of King Idris, whom former Libyan dictator Moammar Gaddafi overthrew in a bloodless coup in 1969.

The Foreign Ministry used the building to provide government services to Libyans and foreigners in the eastern region, which is hundreds of miles from the capital, Tripoli.

The explosion came a day after authorities found and defused another bomb next to the Foreign Ministry in Tripoli, Prime Minister Ali Zeidan said. Speaking to journalists hours after the explosion, Zeidan pledged that the government would track down those responsible and “cut off their hands.”

“There is a force that wants no state and to turn Libya to a battlefield of terrorism and explosions,” he said.

Gaddafi was killed after eight-month uprising that descended into a civil war in 2011. Since then, successive Libyan interim governments have failed to impose law and order. The country continues to be held hostage by unruly militia forces initially formed to fight Gaddafi. The militias, which have huge stockpiles of sophisticated weaponry, now threaten Libya’s nascent democracy.

Zeidan acknowledged the challenge Wednesday, saying that “the security situation is tough.”

On Sept. 11, 2012, al-Qaeda-linked militants stormed the U.S. mission in Benghazi and a nearby building, killing U.S. Ambassador J. Christopher Stevens and three other Americans.

The attack sparked a wave of criticism of President Obama and his administration for its handling of the attack and its aftermath. The administration closed 19 diplomatic posts across the Muslim world for almost a week last month out of caution over a possible al-Qaeda strike, a move seen as a response to the Benghazi criticism.

On Aug. 9, Obama told reporters that the United States was committed to capturing those who carried out the deadly assault and said his government has a sealed indictment naming some people suspected of involvement.

— Associated Press