Six gunmen on motorcycles killed at least 43 people in a passenger bus in Pakistan's southern city of Karachi on Wednesday.
About 60 people, including children, of the minority Ismaili Shia community were said to be travelling on the bus.
Some Pakistani media reports suggest that the death toll is 47, with 24 people injured.
Police said gunmen opened indiscriminate fire on the passenger bus from all sides and some of the injured are in critical condition.
Images of a pink bus covered in bullet holes appeared in Pakistani media, and police also said that some of the assailants got on board the bus and attacked passengers inside.
No one immediately claimed responsibility for the attack but the authorities point to Taliban splinter groups that have attacked religious minorities before.
Two churches and three Shiite mosques were bombed this year in Pakistan, killing 94 people.