Authorities in Bangladesh were evacuating hundreds of thousands of people across its vast coastal region on Monday as a tropical storm approached amid fears of extensive damage.

The government halted operations by all river vessels across the country, closed three airports and asked fishing boats to return from the deep sea and remain anchored in the Bay of Bengal.

The weather office in the capital, Dhaka, said the storm had gusts up to 88 kilometres per hour and was likely to intensify. It was expected to hit the nation early on Tuesday and move across in its southern and southwestern regions, endangering the entire coast.

Bangladesh Storm
A truck leaves Patenga, Chittagong, after fishermen secured their boats as a tropical storm approached (AP/PA)

Since early on Monday, all of Bangladesh has been experiencing moderate to heavy rain, disrupting life throughout the country.

The Bangladesh Red Crescent Society, a partner of the International Committee of the Red Cross, said it has deployed about 1,200 volunteers to help local governments provide emergency service.

The United News of Bangladesh news agency said about 7,000 cyclone shelters have been prepared to house hundreds of thousands of people and their cattle. It said authorities have stocked dry food and medicine.

Many flood protection embankments in southern and southwestern Bangladesh are at risk of being breached by storm surges, endangering villages and farmland, it said.

Bangladesh is a delta nation of more than 160 million people and is prone to natural disasters such as floods and cyclones.