A security academy at Karachi's airport came under attack on Tuesday, less than 48 hours after an all-night siege by Taliban gunmen at Pakistan's busiest airport that killed more than 30 people.
"The ASF academy is under attack. There is gunfire. The extent of the damage is not clear," a senior official at the Federal Investigation Agency said.
It was not immediately clear who was behind the latest attack. A Reuters correspondent near the airport of Pakistan's commercial capital heard gunfire and saw at least four ambulances rushing to the scene.
Pakistani television reported that three militants had been surrounded by security forces at the academy.
All flights in and out of the sprawling city of 18 million were suspended, an official said.
Ten Taliban militants disguised as security force members and armed with rocket-propelled grenades stormed the airport on Sunday night, one of the most brazen attacks in a long-running Pakistani Taliban insurgency.
The assault destroyed prospects for peace talks between the Taliban and the government of Prime Minister Nawaz Sharif and triggered speculation that the army might opt for an all-out offensive against militant strongholds.
Earlier on Tuesday, Pakistani fighter jets bombed Taliban positions on the Afghan border.
"Nine terrorist hideouts were destroyed by early morning military air strikes near the Pakistan-Afghan border," the army's press wing said, adding that 15 militants were killed.
It was unclear if the latest air strikes signalled the start of a broader offensive in the North Waziristan region where the al Qaeda-linked Taliban are based, or indeed if they had been carried out in retaliation for the airport attack.