Thirty people were killed and at least 250 wounded Wednesday when a car bomb exploded in Lahore, Pakistan.
The attack, which occurred on a crowded street during midmorning, is one of the deadliest of the year and is being blamed on the Taliban.
The blast tore through an area about the size of a city block and destroyd cars, smashed brick buildings and left a crater the size of a swimming pool.
Most of the dead and wounded are civilians.
According to reports, gunmen jumped out of a vehicle near a police and intelligence office and opened fire before setting off a powerful explosion when security guards returned fire.
The blast reportedly destroyed the emergency response building at police headquarters, and sheared walls of of a nearby intelligence office.
The attack was linked to the government's recent push to eradicate Taliban fighters from the Swat Valley in the nation's northwest, close to Afghanistan.
"Enemies of Pakistan who want to destabilize the country are coming here after their defeat in Swat," Interior Minister Rehman Malik was quoted as saying.
"There is a war and this is a war for our survival."
No group has officially claimed responsibility for the deadly attack but police have two suspects in custody, and officials have labelled it a Taliban attack.
International security expert Eric Margolis, speaking from Paris, told Canada AM the term "Taliban" is being used to cover a wide swath of groups in Pakistan, from Islamic militants to tribal resistance groups.
He said it's not yet clear whether the Taliban was actually involved, but said it is clear the attack is the direct result of the recent Pakistani military offensive.
"It's certainly a reaction to the Pakistani army offensive in the Swat Valley which has now created, by U.S. figures, 2.3 million refugees," Margolis said.
"It's a huge event that has caused an enormous disturbance across the northwest frontier and it has many Pakistanis enraged at their government."
'Everything went dark'
After the explosion, rescue workers rushed to the scene and scrambled to rescue police officers who were trapped in the rubble of the collapsed buildings.
Inter-Services Intelligence agency officers were among the dead, a senior official told The Associated Press on condition of anonymity because he was not authorized to talk to the media.
People who were on the scene said they felt like they were in the midst of a war zone.
"The moment the blast happened, everything went dark in front of my eyes," witness Muhammad Ali said. "The way the blast happened, then gunfire, it looked as if there was a battle going on."
One of those wounded in the blast said the destruction happened quickly, with little warning.
"All of a sudden we heard a loud sound and the roof collapsed on us," said police official Mohammad Rehman, who was wounded in the attack. "First of all though, we heard the sound of gunfire, then the blast occurred."
Fears of reprisals
There were fears that the large scale operation in the Swat Valley would trigger retaliatory attacks from the Taliban.
The mission is widely seen as an indicator of whether the Pakistani government has the means and resolve to enter into full war with the militants.
The month-long offensive has strong support from the U.S. and Pakistan's other Western allies.
So far 1,100 militants have been killed, according to the Pakistan army.
Wednesday's attack was the third major strike in Lahore in recent months.
With files from The Associated Press
