Identities of the deceased could not be known immediately.
Sub-Inspector Md Mohidul Islam of Nababganj Police Station said a Dhaka-bound bus hit an auto-rickshaw killing two on the spot and injuring another severely.
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After being taken to Upazila Health Complex, the injured woman was declared dead by the doctors, he said.
Police seized the bus but its driver and his assistant fled, said the SI.