Officials said the brazen attack in Karachi, which came three weeks after the US killing of Osama bin Laden, was continuing eight hours after it began late Sunday when up to 15 militants crept in under cover of night.
Around 10 people were wounded and as dawn spread, fire crews battled to douse towering flames that had risen over the PNS Mehran base, the headquarters of the Pakistani navy's air arm in the teeming port city of Karachi.
Interior Minister Rehman Malik said the "terrorists" sneaked into the base from three points adjacent to residential areas in the city of 16 million people, whose port is a vital hub for NATO supplies bound for Afghanistan.
"A building in the premises is still under their occupation from where they are exchanging fire with our soldiers," Malik told reporters Monday.
"The situation is being tackled delicately to secure assets, minimise human losses and defeat the terrorists completely," he said.
"It is not just an attack on a navy establishment, it i