A car bomb outside a building that once housed the US consulate in Benghazi has damaged the Libyan Foreign Ministry building but caused no casualties.

Wednesday's blast in the eastern coastal Libyan city occurred on the anniversary of an attack on the current US consulate that killed four Americans, including the ambassador.

The bomb blew out a side wall of the building, leaving desks, filing cabinets and computers strewn among the concrete rubble, an Associated Press news agency report said.

No group immediately claimed responsibility for the attack.

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

The branch is located along a major thoroughfare of Benghazi.

A Libyan Foreign Ministry official said the US consulate had been located in the building during the reign of King Idris but was closed a few years after Muammar Gaddafi overthrew the monarch in 1969.

'Cowardly terrorist act'

A ministry statement called the bombing a "cowardly terrorist act aimed at attacking the sovereignty of the state and creating an image of chaos".

The ministry official said those responsible for it "want to send a message that diplomatic offices are not secure in Benghazi".

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

Attacks have also targeted diplomats and Western interests.

Much of the violence, including the killing of Chris Stevens, the US ambassador, last year, has been attributed to fighters who are deeply rooted in the region.

Post-Gaddafi chaos

Gaddafi was killed after an 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 remains 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.

Tawfiq Breik, a legislator with the liberal-leaning National Forces Alliance, said that the attacks will continue as long as Libya lacks a strong national army and police.

"Even with so many officials assassinated, no one held accountable," Breik said.

"No one arrested. The state is disabled."

Last year's deadly assault on the US consulate in Benghazi attack prompted a wave of criticism of US President Barack Obama and his administration.

Documents obtained exclusively by Al Jazeera's Investigative Unit revealed that the US State Department knew of the security problems in Benghazi but failed to fix them.

Benghazi fallout

Last month the administration closed 19 diplomatic posts across the Muslim world for almost a week out of caution over a possible al-Qaeda strike - possibly in response to the Benghazi criticism.

On August 9, Obama said the US was still committed to capturing those who carried out the attack. He said his government has a sealed indictment naming some suspected of involvement.

US officials said earlier that the Justice Department had filed under seal the first criminal charges as part of its investigation of the attack.

AP reported in May that American officials had identified five men who might be responsible for the attack.

The suspects were not named publicly, but the FBI released photos of three of the five suspects, asking the public to provide more information about the men.

Some in the photographs are thought to be members of Ansar al-Sharia, the Libyan group whose fighters were seen near the consulate prior to the violence.