At least six people have died after a ferry capsized while caught in a storm in the south of Bangladesh, a government official says.

The ferry, MV Shatil, sank in the middle of a river near Kalagasia, some 200km south of the capital Dhaka, and 19 others were reported to be missing.

"About a dozen passengers survived by swimming ashore. Survivors told us another 25 people were in the ferry when it sank," district government administrator Kazi Sayemuzzamanhe told the AFP news agency.

"Local people have so far recovered six bodies," the official added.

A salvage vessel was headed to the spot to lift the sunken boat, he said.

Ferry accidents are common in Bangladesh, which is criss-crossed with more than 100 rivers.

Most of the accidents occur during the storm season between April and June.

Experts blame poorly maintained vessels and overcrowding for most of the tragedies.