The Pakistani Taliban has claimed responsibility for a gun and car bomb attack in Lahore on Wednesday which killed 24 people.
Nearly 300 people were wounded in the blast.
Officials say gunmen opened fire and threw grenades at the gates of the military's main intelligence agency before blowing up a car bomb when police returned fire.
The bomb brought down a government ambulance service building and damaged the intelligence agency.
A deputy to Taliban leader Baitullah Mehsud told the BBC by telephone the attack was in response to the Pakistani army's operation in the Swat valley.
The caller, who identified himself as Hakimullah Mehsud, threatened similar attacks in other Pakistani cities.
The army is claiming sweeping victories against Taliban insurgents in the Swat valley, near the Afghan border. It says more than 1000 militants have been killed in the past month.