The accident took place around 10:45 pm near Gorakhpur town nearly 270 km from state capital Lucknow.
Krishak Express, travelling from Varanasi to Gorakhpur, rammed the Barauni Express from behind, throwing three of its coaches off the track.
"Railways has suspended the drivers of Krishak Express for overshooting the signal", Railways spokesperson Anil Saxena said.
A probe is on to ascertain the exact cause of the accident.
The derailed coaches have been removed and rescue operations are under way. The injured have been moved to a local hospital.
The Railways has announced a compensation of Rs 50,000 to the families of those killed and Rs 25,000 for those seriously injured in the accident.
Lucknow - 05222233042
Gorakhpur - 05512203265
Chhapra - 09771443941