Suspected militants raided a Navy airbase in Pakistan's southern port city of Karachi on Sunday, killing at least four people, a Naval spokesman said.
An unknown number of gunmen and suicide bombers entered the Mehran-PNS base, a launch site for Pakistani naval helicopters and aircraft, and detonated at least two major blasts, dpa reported.
The attackers were also exchanging fire with the security forces guarding the base.
"We can confirm that the terrorists have attacked the airbase and four people have been martyred there. The terrorists are still inside the base and a commando operation in underway to take them out," a spokesman of the Pakistan Navy said by phone.
Media reports said that the attackers set on fire a US-made P-3C Orion aircraft.
Rehman Malik, the interior minister, confirmed the attack, saying that the terrorists were still present inside the base.
Police and paramilitary forces had cordoned off the base. Television footage showed smoke rising from inside the base.