Eleven Pakistani policemen were killed Thursday when a suicide car bomber struck their bus, the latest in a series of near-daily attacks since the government called for peace talks with militants.
The bombing in the commercial hub of Karachi, which wounded 47 others, came as Pakistan has been negotiating with the Taliban to end a seven-year insurgency.
Munir Sheikh, a senior police official, told reporters the bomber struck in the early morning.
"Apparently it was a suicide car attack as an explosive-laden car hit the police bus transporting officials. So far 11 policemen have died."
Another official, Farooq Awan who heads a special investigative unit, said the bus was making a U-turn after leaving a training centre when a small van struck it.
Doctor Semi Jamali at Karachi's Jinnah hospital confirmed they had received 11 bodies. At least 47 wounded officers were hospitalised and 10 of them were in critical condition, she said.
Police said the blast occurred in an eastern district of Karachi near the national highway.
There was no immediate claim of responsibility for the attack, which was the 11th since Prime Minister Nawaz Sharif announced talks on January 29 and said he wants to "give peace another chance".
Provincial officials vowed the bombing would not deter their campaign to root out criminals and terrorists.
"We are investigating this attack from all angles and who had the most to lose by the forces' actions and want harm upon them. But the forces will not be demoralised and will work more aggressively," Sharjeel Memon, minister for information in the southern province of Sindh which includes Karachi, told reporters.
The Pakistani Taliban have claimed several attacks on security forces in Karachi, including the assassination of the so-called "super cop" Chaudhry Aslam earlier this year.
Karachi, a city of 18 million people which contributes 42 percent of Pakistan's GDP, has also been plagued for years by sectarian, ethnic and political violence.
Pakistan has endured a bloody start to the year with 114 people killed in attacks in January according to an AFP tally.
More than 60 people have died in Islamist-linked violence since Sharif announced the talks.
On Wednesday militants stormed a house of anti-Taliban activists and shot dead nine men in the northwestern city of Peshawar.
On Tuesday a triple grenade attack on a cinema showing pornography in Peshawar killed 13 people.
Both government and militants says they are serious about peace talks but analysts remain sceptical about their chances of success.
Past agreements between the Taliban and the army have proved to be short-lived.
In 2009 the army launched a full-fledged offensive in the northwestern hilly region of Swat, after a two-year local peace deal with the Taliban broke down there.
The hardliners had executed men and flogged women in public during their time in control of the area.
