Surviving passengers aboard the so-called "Friendship Express" say two explosions tore through a pair of cars shortly before midnight Sunday as the train traveled from New Delhi toward the Pakistani border.
Two unexploded suitcase bombs were also found at the scene.
At least 50 people were injured in the incident. Officials say victims may have been trapped in the burning cars, which had bars on the windows for security reasons.
Both Indians and Pakistanis were among the victims. There were a total of 757 people on board the train, 553 of them Pakistanis
Indian Home Minister Shivraj Patil said the act was meant to prevent an improvement in relations between India and Pakistan.
Indian Prime Minister Manmohan Singh expressed "grief and anger," and vowed that those responsible for the attack will be caught.
Pakistani President General Pervez Musharraf said the attack would not be allowed to sabotage a peace process with India.
Information for this story is provided by AP and AFP