Washington has dispatched more troops closer to Libya in the wake of the attack on a US consulate in the North African country so diplomatic personnel can be protected or evacuated in case of any potential threat, the Pentagon has announced.

"We are prepared to respond if necessary, if conditions deteriorate or if we were called upon," Pentagon spokesman George Little told reporters in Washington on Monday.

"Obviously we have moved assets and personnel," he said, without providing any more details.

On September 11, 2012, clashes broke out at the US consulate in the Libyan city of Benghazi after a group of people held a demonstration to protest against a movie deemed offensive to Prophet Muhammad (PBUH).

US Ambassador to Libya Christopher Stevens and three staff members of the US consulate were killed during clashes at the consulate building.

The incident occurred following a massive demonstration held earlier in the day in neighboring Egypt to condemn the anti-Islam movie.

Little added that the additional military forces were stationed at the NATO air base in Sigonella on the Italian island of Sicily.

He went on to say that some of the troops had come from a base in southern Spain, where 500 Marines, troop transport planes, and refueling aircraft were recently deployed.

On May 8, the United States decreased the staff at its embassy in Tripoli, citing the deteriorating security situation.

Britain adopted similar measures after a car bomb attack on the French Embassy in Tripoli injured two French citizens on April 23.

Meanwhile, a car bombing in a hospital parking lot in Benghazi killed at least 15 people, including children, and injured 30 others on Monday.

The blast occurred in a crowded area near al-Galaa Hospital.

Benghazi was the birthplace of the 2011 uprising that toppled long-time Libyan dictator Muammar Gaddafi. It is largely governed by militias in the absence of unified Libyan security and military forces.

The former rebels refuse to lay down their arms, despite efforts by the central government to impose law and order.

Benghazi has been the scene of numerous attacks and assassinations over the past year as the power struggles between militiamen have intensified.