Thirty people have been killed and at least 250 wounded after a suicide car bomber targeted buildings housing police and intelligence agency offices in eastern Pakistan.
The attack, which was followed by gunfire, was the third major strike in the city of Lahore in recent months, and it came amid worries of retaliation from Taliban militants facing a major Pakistani military offensive in the north-west.
Lahore is a major cultural metropolis near the Indian border, and assaults there have heightened fears that militancy in Pakistan is spreading well beyond the north-west region bordering Afghanistan.
No-one immediately claimed responsibility for the bombing.
Raja Riaz, a senior minister in the Punjab province government, told reporters that about 30 people died.
The explosion was so powerful it sheared the walls off buildings in a main business district. TV footage from the scene showed injured bystanders while emergency workers carried at least one person covered by a blanket to an ambulance.
Police official Mohammed Ashfaq said it was a suicide car bomber, and that the attack happened outside the office of the emergency police service in Lahore. TV footage showed the nearby office of the Inter-Services Intelligence agency was also damaged.
Ashfaq said gunshots were heard immediately after the blast. Dozens of troops entered the damaged building of the spy agency to supervise the rescue work, while gunshots were also heard from inside the building even one hour after the blast.
Earlier this year, a group of gunmen attacked Sri Lanka's visiting cricket team in the heart of Lahore, killing six police officers and a driver and wounding several of the players.
A few weeks later, gunmen raided a police academy on the city's outskirts, leaving at least 12 dead during an eight-hour stand-off with security forces including army troops. Pakistani Taliban chief Baitullah Mehsud claimed responsibility for that attack.
