Krishak Express, travelling from Varanasi to Gorakhpur, hit Barauni Express, going from Lucknow to Barauni, from behind at a place seven km from here at around 2300 hours, Chief Public Relations Officer Alok Singh said.
He said there was no death in the incident.
Singh said three coaches of Barauni Express were thrown off the track following the collision, leaving 12 people injured.
Rescue work was in full swing and the injured were admitted to hospital, he said.
Movement of trains on Gorakhpur-Varanasi track has been disrupted following the incident.