A powerful car bomb attack on a police bus on Thursday in Pakistan’s commercial hub of Karachi killed at least 11 policemen and wounded 47 others including 10 in critical condition.

A powerful car bomb attack on a police bus on Thursday in Pakistan's commercial hub of Karachi killed at least 11 policemen and wounded 47 others including 10 in critical condition.

The attack came as Pakistan has been locked into negotiations with the Taliban aimed at ending a seven-year insurgency, with the level of violence in the country showing no signs of abating since talks began at the end of last month.

Munir Sheikh, a senior police official, told reporters the attack took place 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."

Police said that more than 50 officers were on board the vehicle at the time of attack, which occurred in the eastern district of Karachi close to the national highway.

There was no immediate claim of responsibility for the attack, even though Pakistani Taliban have claimed several attacks on the security forces including the assassination of Karachi police senior official Chaudhry Aslam earlier this year.