Fifteen hours after brazenly storming into Pakistan navy's key Mehran airbase in the heart of the port city of Karachi, heavily-armed Taliban militants were still holding onto parts of the base after destroying two US-made surveillance aircraft and killing 13 security personnel. Pakistan army's elite Special Service Group and naval commandos backed by helicopters were hunting down a group of 15-20 militants, who stormed into the sprawling naval complex last night in the worst assault on a military base since the Army Headquarters was besieged in October 2009 in Rawalpindi. The terrorists in a well coordinated attack sneaked into the complex, reportedly housing US-acquired P-3C Orions, long-range maritime reconnaissance planes and Harpoon anti-ship missiles and were locked in continuing gun battle with the security forces. Eleven naval personnel, including a lieutenant, and two paramilitary troopers were killed till noon today, naval spokesman Irfan-ul-Haq told the media. He said, fourteen security personnel – including 11 from the navy – were injured in the skirmishes with the terrorists. Tehreek-e-Taliban Pakistan claimed responsibility for the attack, saying it was part of revenge for the May 2 American raid that killed al-Qaeda chief Osama bin Laden and that their men had orders to fight till death. Unconfirmed reports said, that four terrorists were killed or had blown themselves up while another four were captured by security forces.