At least 23 people have been killed after 10 Taliban militants disguised as security guards attacked Pakistan's Jinnah international airport in Karachi.

A statement from the prime minister's office said that the militants used a cargo terminal to gain access to the country's busiest airport shortly before midnight.

Reports also say that grenades were used in the attack that started around midnight and that security personnel recovered weapons including rocket launchers, petrol bombs and hand grenades from the scene of the attack.

After initially claiming the siege was over, Pakistani security forces have renewed their operation against at least three gunmen still on the loose, with reports of two fresh explosions inside the airport.

Tehreek-e-Taliban, a terrorist group fighting to establish hard-line Islamist rule in Pakistan, took responsibility for the attack.