The Simanta Express train ploughed through the bus and then dragged it at least 500 metres (545 yards) along the tracks at Barobazar town near Bangladesh's western border with India, police inspector Mizanur Rahman told AFP.
"We've recovered 10 bodies while 57 people have been hospitalised -- all of them from the bridal party. Conditions of several people are very critical," Rahman said.
Police said the accident occurred at an unguarded railway crossing, allowing cars and buses to move freely across the track during the early hours of Friday.
Railway police have arrested the guard who was supposed to have been in charge of the crossing, Rahman said, adding train travel between the southern city of Khulna and the country's north has been suspended.