KARACHI - At least one child was killed and dozens of people were wounded in a drive-by bomb attack at an Imambargah in Karachi, police said.

Police said two men on a motorcycle lobbed the bomb as women and children sat outside the Imambargah in the densely populated Liaquatabad district.

"One boy has expired and another boy and a woman are in critical condition," Karachi police chief Mushtaq Meher told Reuters. The deceased has been identified as 13-year-old Faraz s/o Bashir, he said. The injured were taken to the government-run Abbasi Shaheed hospital where doctors said some were in critical condition.

"A women and a child are in critical condition while rest of the injured are stable," Nadeem Rajput, medical officer of the hospital said.

No group immediately claimed responsibility for the attack. Soon after the blast, Shi'ite men and woman gathered outside the mosque and chanted slogans to protest about the lack of security provided to them in Muharram.

The government pledged to crack down on all militant groups following the December 2014 massacre of 134 children at an army-run school in the northwestern city of Peshawar.

It has reintroduced the death penalty, set up military courts to speed convictions and widened its military campaign in lawless tribal areas.