At least nine people, said to be three troops and six militants, have been killed in a terrorist attack on a Pakistani air force base in the country's southern port city of Karachi.

Several military airplanes were also reportedly destroyed. Earlier reports said four foreigners were killed, believed to be US engineers working at the base. But the US embassy says no US nationals were killed. The attack occurred late Sunday night when three explosions were first heard inside the air force base, followed by heavy gunfire.

Local reports said that an estimated 10 to 15 gunmen were involved. So far, nine explosions have been heard inside the base. The Pakistani Taliban have reportedly claimed responsibility for the attack. Prime Minister Yusuf Raza Gilani has condemned it.