News from North Korea is always difficult to get at the best of times. Here's what's being reported, mainly from Chinese sources:

Cause

China has revealed the cause of a train explosion in North Korea was leaking ammonium nitrate, state media reported. "The accident was caused by the leaking of ammonium nitrate in one of the trains," Xinhua cited the Chinese embassy in Pyongyang as saying. It said the embassy had set up a special team to deal with the accident and was providing "essential assistance" to the victims

The trains were reportedly carrying petroleum and natural gas when they collided.

Red Cross, UN Food Agency allowed to help

Pyongyang has accepted help from the United Nations following a serious train crash in North Korea and several aid agencies will be sent to the area, the UN's food agency said today.

A Red Cross official in Beijing said Friday that North Korea has asked the organization to visit the site of Thursday night's massive train collision and subsequent explosion.

Casualties

Up to 3,000 people were killed or injured when two trains loaded with fuel collided and exploded at a North Korean station near the Chinese border, Chinese sources said.

According to a source in the Chinese border town of Dandong, not only was Ryongcheon Station destroyed in the blast, but so were the nearby school and a large number of civilian dwellings; casualties are presumed to be very high, Yonhap News reported.

The source said a Chinese who saw the scene of the accident and returned to Dandong said the area around Ryoncheon Station "had been transformed into ruins, like it was bombed... It was still difficult to grasp exactly how many casualties there were."

The casualty total is presumed to be high, however, since this area -- with a school and a high concentration of houses and apartments -- was totally destroyed.

(UPDATE : the "after" photo has been revealed as incorrect. Thanks to reader Angie Schultz for bringing this to our attention.)

A blast believed to have been caused by explosives on rail wagons has killed 54 people and injured 1,249 people in North Korea, a Red Cross spokesman has said, quoting North Korean authorities.

John Sparrow, a regional spokesman for the Red Cross in Beijing, told Reuters 1,850 households and 12 public buildings were levelled by the blast near the Ryongchon town's centre and another 6,350 homes were partly destroyed.

The figures from Red Cross workers at the scene were the first official figures to emerge more than a day after the disaster on Thursday.

Mr Sparrow said the number of casualties could climb as rescue crews combed through the rubble.

"That figure could increase, obviously," Mr Sparrow said of the death toll after speaking to Red Cross officials at the accident scene.

A collision between two fuel-laden trains triggered the explosion, South Korean officials and media have reported.

Mr Sparrow said the disaster appeared to have been caused by rail cars laden with explosives possibly intended for mining.

China's official Xinhua news agency said leaking ammonium nitrate in one of the trains ignited the blast. Other reports had said two trains carrying fuel had collided.

South Korean media had put the toll at up to 3,000 dead or injured.

The accident happened just hours after reclusive North Korean leader Kim Jong-Il had passed through en route to the capital, Pyongyang, after a rare visit to China.

For North Korea to actually ask for help is unprecedented - things must be truly dire.

Isolated North Korea threw its customary blanket of silence today over an explosion on a rail line in a northern city that may have killed or injured thousands of people.

The opaque Stalinist regime that holds a monopoly on power and views freedom of information as a potential threat to its survival responded to the blast in the northern city of Ryongchon in typically secretive fashion.

Phone links to the outside world were cut, neighbouring countries were starved of information, and a tight news blackout was imposed, according to officials and media reports.

North Korea has yet to break its silence on the explosion which ripped through the railway station at Ryongchon in the north-west of the country, 20km south of the border with China.
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South Korea's government complained of "difficulties confirming details" and Jeong Se-Hyun, the unification minister who handles relations with North Korea, said he had received no official word from Pyongyang concerning the blast.
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Offers of humanitarian aid from South Korea, Australia and the United States were met with silence.

International aid agencies and diplomats based in Pyongyang have also been kept in the dark.

A correspondent for Russia's ITAR-TASS, one of the few journalists from an outside country based in Pyongyang, said that North Korean officials refused to comment on the disaster and North Korea's media was mute.

The only direct confirmation has come from a railway official on duty at Pyongyang station who said there had been an accident near the border with China, ITAR-TASS reported.

"It is a rule for the North Korean propaganda mill not to talk about any accidents," said a North Korean defector based in Seoul who helps run a radio station that broadcasts information into North Korea.

"I've never found out a thing about accidents or disasters through North Korea's media," he said.

Another defector, Jong Yong-Sun, 68, said North Koreans would clam up and refuse to talk about any negative events, fearing the ubiquitous public security agents.
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A Western diplomat based in Seoul said that North Korea was probably in a panic about how to respond to the disaster. A knee-jerk reaction was to try and cover it up.

"To admit it is embarrassing and to admit they need help is probably worse," the diplomat said of the regime that boasts of its self-reliance.

Defectors speak of major disasters in the past that have gone unreported.

In late 1980s, one defector told AFP that a military munitions factory in her hometown, Kanggye, exploded. Many people died, she recounted.

There was never an official death toll and the incident is still unknown to ordinary North Koreans outside the town, she said.

Another major rail disaster went unacknowledged in 1997, when more than 2000 people died after a passenger train plunged off a bridge.

South Korea's Chosun Ilbo newspaper said on its website that North Korea's Ministry of Public Security, in an internal record, put the toll at 2400 dead.

Meanwhile, officials at the North Korean border and hospitals in the Chinese border city of Dandong are denying dealing with casualties from the train crash.

"No, we have seen nothing. Our border post was kept closed all night," an official at the border post near Dandong, said.

Workers at both the Dandong No 1 and No 2 hospitals deny they are treating casualties.

"No, absolutely not. We don't have in our hospital any foreign patients," said a woman doctor surnamed Xiao.

Their denials are echoed by the local government.

"I have never heard of this," said a government official surnamed Li.

Seoul officials told Yonhap news agency early today they have confirmed up to 3,000 casualties are being taken to hospitals in Dandong just over the border and other areas.