Hundreds of people, including top local officials, have been killed in a massive freight train blast in Iran.
The explosion left an untold number of people injured
The train exploded in the north-east of the country, leaving up to 295 dead near the town of Neyshabur in Khorasan province on Wednesday morning.
Hundreds more were injured when wagons carrying sulphur, petrol and fertiliser derailed, caught fire and blew up.
Nearly 200 of the dead are thought to be rescue workers who were fighting the fires when the blast occurred.
According to Iranian TV, the train wagons - which included 17 wagons of sulphur, six wagons of petrol, seven wagons of fertilizers and 10 wagons of cotton wool - broke loose from a train station and rolled about 20km (12 miles).
Then they derailed and caught fire at 0400 local time (0030 GMT).
Fire-fighters had nearly put out the blaze when an explosion occurred at 0935.
The blast was so powerful local residents thought it was an earthquake - and Iranian seismologists recorded a quake of magnitude 3.6 at the time of the explosion, AP reported.
Homes in nearby villages were flattened by the force of the blast, AP said.
Some villagers are believed to have been trapped in the ruins of their mud-brick homes, raising the possibility that the death toll could be even higher.
The blast could have been due to fumes from the cargo on board the crate wagons.
Some sources say the train wagons were set loose by earth tremors.
More than 40,000 people died in an earthquake on 26 December in the ancient city of Bam in the south-east of the country.
An investigation is now under way into how the accident happened.
A BBC correspondent in Iran says serious questions are also likely to be raised about how such a volatile and deadly mix of materials could have come to be transported in the same convoy.
"The scale of the accident is very extensive and the damage seems to be more than initial estimates suggested," said local official, Vahid Barakche.
"The whole town is shocked by this accident," the editor of a local newspaper, Saeed Kaviani, told AP news agency.
The cars may have been set loose by earth tremors
"Official vehicles mounted with loudspeakers are roaming the city calling for volunteers to donate blood."
Mr Kaviani said dozens of people remain buried under the rubble of their homes in the nearby villages.
The blast shattered windows more than 10km (six miles) away and could be heard in the regional centre of Mashhad, 75km from the scene.
TV pictures showed massive destruction, with derailed wagons on fire and choking black smoke.
Top city officials, including the local governor, mayor and fire chief, are believed to be among the dead.
Irna news agency also said the head of the city's energy department had been killed and that the director-general of the provincial railways was missing.
World's worst train disasters
June 2002: Dodoma region, Tanzania - at least 200 killed when passenger train collides with goods train
Feb 2002: Egypt - 300 killed in fire on train travelling to Cairo
June 1989: Ufa, Russia - More than 400 killed in gas explosion under two trains
Aug 1995: Uttar Pradesh, India - 300 killed in train collision
June 1981: Bihar, India - 800 killed when cyclone blows train into river
An Irna reporter was also killed in the blast.
Several hundred injured people have been taken to hospitals in Neyshabur and Mashhad.
An official from the Natural Disasters Headquarters in Neyshabur, said the hospitals had been overwhelmed with casualties.
UN Secretary General Kofi Annan has offered United Nations assistance to those affected by the explosion.
"The secretary general was distressed to learn of the casualties and damage," Mr Annan's spokesman said in a statement.
The disaster comes at a time of political uncertainty in Iran, with controversial parliamentary elections to be held on Friday.