Large explosion in the city of Pakistan

A suicide car bomber has attacked police headquarters in the Pakistani city of Lahore, killing at least 23 people and injuring 200, police say.

The blast destroyed a police emergency response building, gutting vehicles outside, and an office of the ISI intelligence service was also damaged.

It is feared the death toll may rise further as casualties are brought out from beneath the rubble.

Attacks on Pakistan's second-largest city have been blamed on the Taliban.

Pakistan's army has been battling the insurgents in their stronghold in the Swat valley, in the north-west, and there have been fears of Taliban retaliation, the BBC's Barbara Plett reports.

Bulldozers

Rescuers speaking unofficially put the death toll at 35, although this figure is unconfirmed.

Issam Ahmed, a journalist with the Dawn newspaper in Lahore, arrived at the scene about 20 minutes after the blast.

He told the BBC he could still hear shots in the area, as security forces apparently exchanged gunfire with militants.

A least two arrests were made in the area.

Rescue workers were seen clambering over a pile of concrete which was all that remained of the emergency response headquarters.

They were able to drag out several of the injured. Semi-conscious policemen could be seen being carried out in blood-stained uniforms.

Debris was scattered on the road outside. Officials were seen rushing towards the buildings to cordon off the area.

The blast also destroyed several cars parked or standing on the main Mall road opposite to the police building.

Bulldozers and other heavy lifting equipment were brought in as many people were feared to be trapped under the debris.

'Surreal scene'
Zubair, a BBC News website reader in Lahore, described hearing the explosion: "I was sitting in my office on Lawrence Road [about 500m from the site] when a huge explosion rocked our entire building.

"Glass windows shattered to pieces and the ceiling came down on the floor. I ran outside the building to nearby Jinnah Garden. I could hear gunfire which lasted for about 10 minutes and then I saw ambulance and police rushed to the scene."

Matthias Gattermeier, an Austrian reader also in Lahore, said his office building had been shaken so hard he thought it would collapse.

"We first thought the explosion happened far closer by, but the blast was just so massive," he said.

"I ran out of the building and saw a surreal huge ring of white smoke rise into air. Within minutes police and military blocked the streets. Disaster units and emergency are going in and out in every minute. The streets are full of people."

Lahore, Pakistan's second-largest city, has seen bomb attacks with increasing frequency.

Weeks before a police college was attacked in March, with eight people killed, militants attacked the Sri Lanka cricket team in the city, killing six police guards.