The blasts ripped through the RA Bazaar, which lies in a neighbourhood where several security agencies have facilities.

More than 100 people were wounded in the explosions, officials added.

Sky's Asia correspondent Alex Crawford said police in Lahore told her there were two suicide bombers.

"Both arrived on foot at a bus stop, which was situated in a market area inside the army residential area of Lahore," she said.

"The first one saw an army patrol van coming along the road and he stepped out in front of it and blew himself up.

Seconds later, the second bomber detonated his device.

Crawford added that large crowds had been gathering for Friday prayers at the time and that "is why the casualties are rising".

Police said a third explosion hours later did not result in any serious casualties.

Six security personnel were among the dead, police official Chaudhry Mohammad Shafiq said.

Pakistani TV channels showed security forces swarming the area as bystanders rushed the injured into ambulances.

Eyewitness Afzal Awan said he saw several people, some missing limbs, lying in pools of blood.

"It was a big blast. I saw smoke rising everywhere. A lot of people were crying," Mr Awan told TV channels.

No group immediately claimed responsibility, but suspicion quickly fell on the Pakistani Taliban and al Qaeda.

The militants are believed to have been behind scores of attacks in US-allied Pakistan over the past several years.

They include a series of strikes that began in October and killed some 600 people in apparent retaliation for an army offensive along the Afghan border.

More recent attacks had been smaller and confined to remote northwest regions near Afghanistan.

But, on Monday, a suicide car bomber struck a building in Lahore where police interrogate terrorist suspects. At least 13 died and dozens more were wounded.