At least 64 people have been killed and more than 250 injured in northern India after a passenger train derailed, while a railway bombing in the east of the country has caused another derailment, injuring at least 50.
In Sunday's first incident, the packed Kalka Mail train carrying passengers from Kolkata derailed as it was approaching the town of Kalka in Uttar Pradesh.
The train was reportedly moving at more than 100km per hour when 12 coaches and the engine jumped the tracks, AK Jain, a senior railway official, said.
He said he feared the death toll would go up. The number of passengers on board the train was not known.
Meanwhile, in the eastern state of Assam, a bombing caused four carriages of an express train to derail near Ghagrapara, 65km from the city of Guwahati.
Medical personnel headed to the site of the accidental derailment in Malwa, a town about 120km southeast of Lucknow, the capital of Uttar Pradesh.
The accident disrupted rail traffic on the Delhi-Howrah route, according to railway officials.
The site of the was a pile of twisted metal. At least one coach flew above the roof of another ahead of it and was dangling precariously, television footage showed.
Another coach was thrown away from the rest of the train.
Al Jazeera's Prerna Suri, reporting from New Delhi, said: "The cause for the derailment is still unknown but initial reports suggests that the driver had to apply emergency brakes for some reason. Because of that several coaches collapsed into each other."
Indian media reports said the train was travelling at about 105km per hour when the derailment occurred.
HC Joshi, a senior railway official, told the CNN-IBN news channel that rescuers were struggling to free at least five people pinned under the wreckage of one of the worst-damaged coaches.
Joshi said "13 bogies ... have derailed of which 10 are in very bad shape. The exact cause of the derailment could not be ascertained yet as we are busy in rescue operations".
He said a high-level investigation had been ordered into the incident.
The federal railway ministry announced a compensation of $11,000 for the families of those killed in the accident.
Express trains normally carry about 1,000 people and travel at speeds of 100-130km per hour.
India's railroad network is one of the largest in the world and carries about 14 million passengers a day.
Accidents are common, with most blamed on poor maintenance and human error.
Indian Railways, a state-run monopoly, has a patchy safety record because of ageing infrastructure.
On July 7, at least 31 people were killed when a train rammed into a bus driving over a level crossing which did not have a gate or an attendant - typical of several such crossings in India.
Latest government data showed that 336 people were killed and 437 injured in rail accidents between April 2010 and mid-January 2011.
Source: Al Jazeera and agencies