At least 19 people were killed and an estimated 1,500 fishermen are missing after tropical storms smashed into Bangladesh's southern coastal islands and districts early Thursday, police said.

Police said at least 1,500 mud, tin and straw-built houses were also levelled in the storms that swept Bhola, Hatiya and Sandwip Islands and half a dozen coastal districts after Wednesday midnight.

At the worst-hit island of Hatiya, at least seven people were killed after they were buried under their houses or hit by fallen trees, said local police chief Moktar Hossain. More than 1,000 houses were flattened.

"More than 100 fishing trawlers, each carrying at least 10 fishermen, have been missing since the storm," he told AFP, calling it one of the most powerful in decades.

Many fishermen are expected to have taken shelter in other remote islands in the Bay of Bengal or in the neighbouring Sundarbans, the world's largest mangrove forest.

In the past, many fishermen thought to be missing from storms returned home to coastal villages a week or two later.

Four people were killed in Bhola, three each in Sandwip and Companyganj and two at Char Jabbar, police said.

The police chief of Bhola district, Bashir Ahmed, told AFP more than 500 fishermen were missing from the country's largest island and at least 500 mud and straw-built houses were levelled by the sudden storm.

Bangladesh's weather office forecast heavy rain in the coastal region and advised fishermen to take care near the shore, but there was no major storm warning.

"We only got the warning signal number three. But the storm was so powerful, the weather office should have hoisted the signal number seven or eight," said Ahmed, referring to the intensity of the storm on a scale of ten.

"It caught the fishermen and coastal people by surprise. Till now we haven't had any reports from the missing fishermen," he said, adding the authorities had sent relief to thousands of affected people.