Media playback is unsupported on your device Media caption The attack happened as the bus left a police training centre in Karachi

A bus carrying Pakistani police officers has been targeted by a suspected suicide bomber, killing at least 11 people on board.

More than 40 others - mostly police officers - were wounded in the early morning attack in Pakistan's southern city of Karachi.

The bus was hit by an explosives-laden vehicle as it was leaving a police training centre, officials said.

Karachi is Pakistan's biggest and most lawless city.

Hundreds of policemen have lost their lives fighting militants and criminal gangs linked to the city's main ethnic, political and sectarian parties, the BBC's Shahzeb Jillani reports from the city.

Thursday's attack - which no one has yet claimed responsibility for - is one of the bloodiest on police in Karachi in recent months, our correspondent says.

Peace talks

Police said more than 50 officers were on board the bus as it prepared to leave a training centre in the east of the city.

"Apparently an explosive-laden car hit the police van transporting officials," police official Muhammad Iqbal told the AFP news agency.

Local TV channels showed broken glass and pieces of vehicles scattered around the scene of the blast.

Doctors at the city's Jinnah hospital confirmed they had received 11 bodies and said at least 10 of the wounded officers were in a critical condition.

The latest attack comes amid talks between the government and the Pakistani Taliban to try and negotiate a peace deal.