An explosion on a train headed from India to Pakistan started a fire that swept through two coaches, killing at least 65 passengers. Dozens more people were injured.
Authorities say two suitcases packed with unexploded crude bombs and bottles of petrol were found in train cars not hit in the attack, leading them to believe the fire was set off by an identical explosive device.
"This is an act of sabotage," Railway Minister Laloo Prasad told reporters in Patna, India. "This is an attempt to derail the improving relationship between India and Pakistan."
India's junior home minister, Sriprakash Jaiswal, said the homemade bombs were not powerful and were simply intended to start a fire on the train a day before Pakistani Foreign Minister Khursheed Kasuri was to arrive in New Delhi for talks on the ongoing peace process.
Jaiswal called the attack part of a "conspiracy ... to disturb communal harmony, India's stability and to disturb the peace process between India and Pakistan."
The fire engulfed two coaches of the Samjhauta Express, one of two train links between rival India and Pakistan. Because of security concerns, the train is kept sealed - with locked doors and barred windows in the lower-class coaches - from New Delhi to the border, and passengers may have been trapped inside the burning cars.
The fire broke out just before the train reached the station in the village of Dewana, 50 miles north of New Delhi.
People who live near the tracks rushed to the train with buckets of water soon after the fire broke out, and the blaze was eventually extinguished after fire trucks arrived.
Speaking to reporters at the scene, Bharti Arora, superintendent of the Haryana state railway police, said the death toll had risen to 65.
At least 30 passengers who were burned or injured in the blaze have been taken to hospital in the nearby town of Panipat, the general manager of the Northern Railway, V.N Mathur, told reporters.
The dead included both Indians and Pakistanis, officials said.
The train was travelling from New Delhi to Atari, the last station before the border with Pakistan.
At Atari, passengers change trains in a special station, switching to a Pakistani train that takes them to the Pakistani city of Lahore.
The train links are one of the most visible results of the peace process under way between nuclear-armed India and Pakistan, and one of the easiest ways to travel across the heavily militarised border.
Frantic relatives flocked to New Delhi's main railway station this morning in search of answers. But there was only a handwritten list, posted on a bulletin board, with the names of 13 injured people and one identified corpse.
Mohammed Wasim Khan, who had dropped off his uncle and two young nephews at the station last night, said railway officials had brusquely told him to take a train to the scene of the blast if he wanted more information.
"What am I going to tell my cousins?" he said, crying. "What will I tell them?
Relations between India and Pakistan have warmed in recent years, although they nearly went to war following a 2001 attack on the Indian Parliament that India blamed on Pakistan. The two now hold talks regularly.
The enmity between India and Pakistan centres around Kashmir, a largely Muslim Himalayan region divided between the two countries but claimed in its entirety by both.
More than a dozen militant groups - most based in Pakistan - have been fighting in Indian Kashmir for nearly two decades, seeking independence for the region or its merger with predominantly Islamic Pakistan. More than 68,000 people, most of them civilians, have died in the violence.
Within hours of the fire, authorities detached the burned coaches and the rest of the train left for the India-Pakistan border.
Indian security forces were put on alert after the fire, and police swarmed many stations, but train service continued.
Today's blaze immediately revived memories of earlier train deaths, including train bombings on Mumbai's commuter rail lines last July that killed more than 200 people.
Police say Lashkar-e-Tayyaba, or Army of the Pure, a Pakistan-based Islamic militant group, as well as the Students' Islamic Movement of India, a banned group based in northern India, were behind those blasts. Officials also have alleged that Pakistani intelligence was involved in the attacks, but Pakistan has repeatedly denied the accusation.
In 2002, Hindu-Muslim riots broke out after a train fire killed 60 Hindus returning from a religious pilgrimage.
Muslims were blamed for the fire in the western state of Gujarat, and more than 1,000 people, most of them Muslim, were killed by Hindu mobs. About 84 per cent of India's more than 1 billion people are Hindu, and Muslims account for about 14 per cent.Reuse content