Maritime ports of Chittagong, Cox's Bazar, Mongla and Payra have been advised to keep hoisted distant cautionary signal No 1 as the depression over the southwest Bay of Bengal and adjoining Sri Lanka coast intensified into a deep depression over the same area.
It was centred at 9am on Thursday, about 2035 km southwest of Chittagong port, 1975km southwest of Cox's Bazar port, 1945km southwest of Mongla port and 1930km southwest of Payra port, said a special bulletin of the Met office.
It is likely to move north-northwestwards and intensify further.
Maximum sustained wind speed within 48km of the Deep Depression centre is about 50kph, rising to 60kph in gusts or squalls.
The sea will remain rough near the Deep Depression centre.
All fishing boats and trawlers in North Bay have been advised not to venture into the deep sea till further notice.