Pakistan was Tuesday investigating a brazen assault on a naval base in Karachi, raking over clues in a bid to identify the attackers who carried out the siege, two of whom may have escaped.

It was the worst assault on a military base since the army headquarters was besieged in October 2009, piling further embarrassment on the armed forces three weeks after Osama bin Laden was found living under their noses.

"A joint investigation team has started the investigation," one security official told AFP on condition of anonymity.

Up to six Taliban fighters, armed with rocket-propelled grenades, explosives and automatic rifles, crept under cover of darkness to place ladders against the walls of the Mehran base and climbed over barbed wire into the facility.

In a 17-hour standoff they managed to destroy two P-3C Orion surveillance aircraft, costing an estimated $36 million, which had only been delivered by the United States a year ago, and killing 10 security personnel.

Although the Pakistani Taliban claimed responsibility, government official Sharfuddin Memon from the southern province of Sindh, of which Karachi is the capital, said the attackers had not yet been identified.

Security officials say they are piecing together how the well-planned attack unfolded and how the attackers worked hard not to be spotted.

"We have not found any video. The attackers succeeded in dodging the cameras," one official said.

An AFP reporter saw stepped up security around the Mehran base on Tuesday while visitors were barred from a nearby Pakistan Air Force museum.