The deadly collision took place at an unmanned crossing in the town of Kushinagar in Uttar Pradesh, the Indian news agency ANI said.
At least children died in the incident, according to a report by New York Post.
Top police officer O.P. Singh says the bus driver also was killed in Thursday's accident, Fox News reports.
Officials reportedly said 18 people were on the bus, seven of them are in critical condition and the death toll may rise.
The survivors of the incident were reportedly taken to a hospital in Kushinagar.
Uttar Pradesh chief minister Adityanath is reportedly on his way to the accident site for an on-the-spot assessment.
He already expressed his deepest condolences, and directed the district administration to provide all help and medical aid to the injured, the Times of India reported.