Unidentified armed robbers struck the Azeemabad Express and looted passengers after assaulting them while the train was travelling between Bihar and Uttar Pradesh early on Saturday, officials said.
A case was later registered at a government railway police (GRP) station in Mughalsarai in Uttar Pradesh, where the train arrived on Saturday morning.
The robbers looted the passengers at around 3am at Buxar railway station in Bihar and managed to escape after pulling the train's emergency chain, officials at the Mughalsarai GRP station said.
"We have registered a case against 10-12 unidentified men. Some of them even had guns," GRP inspector Tripurari Pandey told reporters in Mugalsarai of Chanduali district, some 350 km from Lucknow.
"According to the passengers, the robbers primarily targeted two sleeper coaches of the train. We are yet to ascertain the exact amount of cash and other valuables looted," he added.
According to preliminary investigations, the robbers entered the train in Chausa in Bihar.
"Though the robbers assaulted a number of passengers, mostly those who refused to hand over their money and valuables, none of them received any serious injury," Pandey said.
The train was heading to Ahmedabad from Patna.