China and South Korea have each already offered over $US1 million in emergency aid to their impoverished neighbour, while help has also been offered by Australia, the United States and the European Union.
The massive explosion, at Ryongchon train station near the Chinese border, was caused by an accident involving two train carriages packed with inflammable material on Thursday.
World Health Organisation aid worker Eigil Sorensen said buildings had been destroyed up to 500 metres from the blast site and windows had been blown out over a 10-kilometre radius.
The aid workers were invited to assess the devastation after North Korea made a rare appeal for international help.
North Korean officials acknowledged the explosion for the first time yesterday, saying at least 154 people were killed – including 76 children – and 1300 were injured in the blast.