A Chinese news agency has reported officials in North Korea as saying 150 people have been confirmed dead and some 1,300 injured in the train blast in Ryongchon.
The authorities say 76 students were among those killed.
It is the first time that North Korea has officially acknowledged the blast, which is thought to have been caused when a live power cable came into contact with two freight wagons loaded with explosives.
A United Nations aid mission is on its way to the scene of the rail disaster.
The mission involves UN agencies, International Red Cross, non-governmental groups and diplomats.
