Meanwhile, authorities in neighbouring Bangladesh braced for the storm, evacuating tens of thousands of people from their homes on the southwestern coast.
"We have mobilised medical teams who are on standby, and we have food and drinking water provisions ready if needed," Abdus Samad, chief of the Satkhira district, said.
Cyclones and tropical storms are common in Bangladesh, killing many people in the delta nation of 150 million every year, and causing huge damage to crops and property.
Cyclone Sidr swept parts of the Bangladesh coast in November 2007, killing about 3,500 people. A cyclone killed about 140,000 people in April 1991.