At least 65 people have been killed after a bomb attack aboard a train travelling from India to Pakistan.
The fire engulfed two carriages on the Samjhauta (Friendship) Express
Passengers said they heard two blasts as the train passed near Panipat, about 80km (50 miles) north of Delhi. A fire then swept through two carriages.
The train is part of the "Friendship Express" service that takes passengers from Delhi to Lahore in Pakistan.
Indian and Pakistani leaders denounced the attack as an act of terrorism aimed at disrupting their peace process.
The blasts happened a day before Pakistan's foreign minister was due in Delhi for talks with Indian leaders.
The minister, Khurshid Kasuri, said the explosion was a "horrendous act of terrorism" but it would not change his plans to visit India from 20-23 February.
Pakistani President Pervez Musharraf called for a full investigation by the Indian authorities but said the attack would not undermine peace efforts between the two nations.
"Such wanton acts of terrorism will only serve to further strengthen our resolve to attain the mutually desire objective of sustainable peace between the two countries," the president said in a statement.
Indian Prime Minister Manmohan Singh, expressing "anguish and grief" at the loss of life, vowed that the culprits would be caught.
The reaction from both governments suggests the prime suspects might be groups such as Lashkar-e-Toiba and Jaish-e-Mohammad, the main Islamic militant groups who have been blamed for many high-profile bombings, says the BBC's Jill McGivering.
Recent attacks on Delhi, Mumbai and Varanasi, for example, seemed designed to damage India's image abroad and stoke anti-Pakistan feeling inside India.
But the fact that so many of the dead on the train were Pakistani Muslims may indicate that the devices were intended for a different target, or exploded prematurely, she says.
The twice-weekly service from the Indian capital to Lahore was restarted in 2004 after a two-year gap as part of the peace process between the two countries.
More than 500 people were believed to have been on the train, the majority of them Pakistanis.
'Suffocated to death'
Two carriages were shaken by blasts at about midnight (1830 GMT Sunday) as the train was passing through the station in the village of Deewana in Haryana state.
It shuddered to a halt and a ball of fire then engulfed the two coaches.
Service restarted in January 2004
Connects Delhi and Lahore, via Atari
Runs twice a week
One of a series of measures easing travel restrictions
Witnesses said they saw people screaming and struggling to get out.
The injured were pulled out of the burning carriages onto the trackside by fellow passengers, and local residents rushed to help.
"I heard a loud explosion and then it was all smoke," passenger Tara Chand was quoted by Reuters news agency as saying.
"Looking at the intensity of the smoke, many people must have suffocated to death before being charred."
The BBC's Soutik Biswas, reporting from the scene, said the heat of the flames had peeled the blue paint off the coaches, and oil and cinders covered the tracks.
He went into one of the carriages and saw boxes of food and spices that many of the passengers would have been taking as gifts to friends and relatives in Pakistan.
Shiv Ram, a police railway constable, was one of the first officials on the scene.
"The coaches were totally engulfed in flames. I brought out three charred women - I could only recognise them as women because they were wearing bangles," he said.
Police said they had found explosive devices at the scene.
The burnt-out carriages were moved to a railway siding a couple of kilometres away for forensic examination.
Anxious families gathered at Delhi's main rail station for information
The rest of the train continued on its journey to the border station of Attari where passengers switched to another train to travel on to Lahore.
Most of the bodies were charred beyond recognition and the mortuary at the local hospital in Panipat is overflowing.
Mohammad Saif, from Delhi, went to the site and the local hospital in search of his aunt and niece, who been visiting him from Pakistan.
"I saw them off at the Delhi railway station last night about 9pm. There was no security, no checking, nothing at the station. I've been looking for them, can't trace them," he told the BBC.
Anxious families rushed to the main railway station in Delhi where there was a handwritten list of some of the people known to have been injured.
The Indian High Commission in Islamabad said arrangements were being made to process visas immediately for Pakistanis who had relatives on the train and wished to go to India, Reuters reported.