Pakistani police say a bomb blast at a railway station in the eastern city of Lahore has killed at least three people and injured 20 others.

Several of the wounded were hospitalized in critical condition.

Officials say the bomb exploded Tuesday outside a waiting room at the city's main station.

A senior police official told Reuters news agency that six to eight kilograms of explosives were planted in a bag left near one of the counters at the station.

Islamist militants have carried out bombings across Pakistan in retaliation for military operations targeting insurgent groups in recent years.

Lahore is the capital of Pakistan's Punjab province.