The incident occurred at 3.45 am (local time) in southwestern region at Jhenaidah's Kaliganj area, police said.
Following the incident, railway services between Khulna and the rest of Bangladesh remained badly hit for around seven hours, reported bdnews24.Com.
Officials said the ill-fated bus, which was carrying people returning from a wedding ceremony, got smashed by 'Simanta Express' train and was dragged to at least one kilometre before coming to a halt.
Local people, fire service and police began rescue operations and retrieved nine bodies, mostly of children and women from the spot.
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Thirty of those wounded were taken to Jessore Medical College and Hospital and the rest were admitted to hospitals in Jhenaidah and Kaliganj.
One of them died at Kaliganj hospital while doctors said 10 others were in critical condition. Another death was reported later.
"11 people have died so far as the death toll may rise further," an official was quoted by media as saying.
Such road accidents are frequent in Bangladesh as the blame goes to the poor maintenance and human errors.