A bomb hidden in a motorcycle exploded killing at least 11 people, mostly aged between six and 15, at a football match in the Pakistani city of Karachi.

The remote-controlled device was detonated late at night at the end of a local tournament at a pitch in the rundown Lyari neighbourhood.

No group has claimed responsibility for the blast that injured at least 24 people.

The bomb went off as a packed stadium was watching the prize-giving ceremony at the end of the last match of a tournament held throughout the fasting month of Ramadan.

"When the match ended, we came out and as soon as we came out there was a blast," Ameer Ali, who was injured in the blast, told Reuters.

"Everyone started running in panic. Many people were hit, which scared everyone."

Pakistani authorities have launched an investigation into the explosion.

It has been suggested that the target of the attack may have been a provincial minister named Javed Nagori, who was at the stadium.

Nagori was reportedly walking towards his car as the bomb went off.

Karachi has long been affected by bloody turf wars and political violence. Taliban influence has also been growing in the area.

A 13-year-old girl was killed in a separate explosion that wounded more than 20 people in southwestern Pakistan.

The area is home to both Islamic militants and separatists who have been waging a low-level insurgency against the government for decades.