Pakistan lull ends as 12 die in bomb blast

The attack shattered what had been a relative lull in major violence in Pakistan. It also showed that rebels retain the ability to strike the country's heartland, far from the Afghan border regions where al-Qaida and the Taliban have long thrived, in spite of army offensives aimed at wiping them out.

No group immediately claimed responsibility, but suspicion fell on the Pakistani Taliban and allied militant groups.

The groups are believed to have been responsible for a wave of attacks which killed more than 600 people starting in October, including several in major Pakistani cities. More recent attacks have been smaller and confined to remote north-west regions near Afghanistan.

The latest explosion comes amid reports of a Pakistani crackdown on Afghan Taliban and al-Qaida operatives using its soil. Among the militants said to have been arrested is the Afghan Taliban's number two commander, Mullah Abdul Ghani Baradar.

The bomb went off outside a Punjab province police building, said police official Zulfikar Hameed. TV footage showed a huge crater in the ground where the blast seemed to have originated. It appeared the suicide bomber rammed a car packed with as much as 1,300lb (600kg) of explosives into the building's perimeter wall, officials said.

Lahore police chief Pervez Rathore said: "This place was used to interrogate important suspects but presently there was no such suspects, but more than 40 staff were manning the place."

Pakistanis in the neighbourhood had filed complaints urging authorities to move the unmarked interrogation unit out of the residential area so the street would not become a target for an attack, said Mohammad Musharraf, who lives nearby.

"My whole house was shaken and I thought it was an earthquake," he said. "A window dislodged and fell on my son, fracturing his arm."