A powerful explosive device was defused on Wednesday on board a train in Pakistan that had passed through Lahore railway station at the time of a bomb blast that killed three persons and injured over 50 others.

A bomb disposal squad defused the device found on the Peshawar-bound Awami Express at Attock railway station.

The bomb was discovered when a passenger drew attention to a suspicious looking bag, TV news channels reported.

The bag had a bomb inside that contained between 15 and 20 kg of explosives and was packed with ball bearings, officials told the media.

The train was allowed to continue to Peshawar after the bag with the bomb was removed and all coaches were thoroughly checked by security officials.

Shortly after the same train pulled into Lahore railway station Tuesday evening, a bomb went off on a crowded platform, killing three persons and injuring over 50 others.

A railway police official and a witness said the explosion occurred when a porter was removing a bag from the train.

The porter was among those killed.

The Awami Express originates in Karachi, the capital of the southern Sindh province, and goes to Peshawar, the capital of Khyber-Pakhtunkhwa province in Pakistan's troubled northwest.