But in the first confirmation of the disaster from inside North Korea, a spokesman for the International Federation of the Red Cross in Beijing quoted North Korean Red Cross officials as saying at least 54 people were killed in the apparent collision and 1,249 others injured.
Spokesman John Sparrow said he received the information from North Korean colleagues who visited the site of the disaster in the city of Ryongchon, some 20 kilometers from the Chinese border.
Some reports say two freight trains carrying inflammable liquids collided, while others say one train carrying dynamite was the source of the explosion.
Sparrow said he expected the toll to rise as many of those affected could be stuck under the rubble of buildings that were apparently flattened in the explosion.
"The official death toll is now 54. That is a provisional figure," Sparrow said. "The number of people wounded is 1,249 -- which is a figure that we expect to rise because we have also been told that 1,850 households have been totally destroyed [and] that 6,350 households have been partly destroyed."
Russia's Foreign Ministry also claims to have received confirmation of the blast from its diplomatic contacts in North Korea. Foreign Minister Sergei Lavrov said the North Korean Foreign Ministry had promised to provide Russian Embassy officials with further details as they became clear.
Earlier, South Korean media, which have given the most detailed information about the mishap, said two freight trains -- one carrying gasoline and the other liquefied petroleum -- collided at the main train station in Ryongchon, causing a violent explosion.
But it now appears only one train may have been involved, which was actually loaded with dynamite. The head of the UN's World Food Program in North Korea told the AFP news agency that the explosion occurred when two train cars loaded with dynamite were being shunted onto a siding and hit live electrical wires.
The city of Ryongchon is a rail hub and an industrial center, with a population of more than 100,000. The train station is located in the center of the city.
The wreck occurred just nine hours after North Korean leader Kim Jong-il -- aboard his personal train -- passed through the station on his return from a visit to China.
But South Korea's Unification Minister, Jeong Se Hyun, told reporters in Seoul today there did not appear to be evidence of foul play. "There's no evidence [of an assassination attempt on Kim]. Unexpectedly, accidents can lead to big disasters," Jeong said.
In Geneva, a spokeswoman for the United Nations World Food Program, Christiane Berthiaume, said North Korean authorities have now given permission for UN relief agencies to travel to Ryongchon. The agreement followed two meetings between North Korean government officials and the World Food Program's representative in the country.
U.S. State Department spokesman Richard Boucher, speaking yesterday, said Washington -- which has termed North Korea as part of the "axis of evil" -- would be prepared to provided humanitarian assistance, if asked.
"We've always been willing to help the people of North Korea with humanitarian needs, but I'm not aware -- I don't think we know enough about the situation yet to know whether there is any assistance that we have that might be necessary," Boucher said.
Sparrow said that across the border, the Red Cross in China was ready to provide any medical help necessary, but so far none had been requested.
"Hospitals [in Dandong, China] have certainly been placed on alert, close to the [Chinese-North Korean] border, and the Chinese Red Cross is now on standby to help there should that be necessary," Sparrow said.
Although the exact details of the North Korean rail disaster remain unclear, it calls to mind a deadly Iranian train wreck in February, in which rail cars loaded with fertilizer, petrol, and sulphur products caught fire and subsequently exploded, killing more than 300 people and devastating five villages.