The Press Trust of India news agency says 15 passengers died at the scene on the outskirts of Gorakhpur, a town 270 kilometers (170 miles) east of Lucknow, the capital of Uttar Pradesh state. It says another five died in hospital.
It quoted district administrator Ravindra Naik as saying that at least half a dozen people injured in Sunday's accident were in critical condition.
Officials could not be immediately reached.
Road accidents are common in India - many due to negligence, bad roads and aging vehicles.
