The low-lying areas of 15 coastal districts in Bangladesh, including their offshore islands and chars, are likely to be inundated by tidal surges, the weather department said on Friday.

These districts are Satkhira, Khulna, Bagerhat, Jhalakathi, Pirojpur, Barguna, Patuakhali, Bhola, Barishal, Laxmipur, Chandpur, Noakhali, Feni, Chattogram and Cox's Bazar.

The well-marked low over the northeast Bay moved northwestwards and intensified into a depression over the northeast Bay and adjoining areas around 6am, according to Bangladesh Meteorological Department.

Read: Depression in Bay: Low-lying areas of 4 districts inundated

The depression is likely to intensify further and move northwestwards.

The sea will remain rough near the depression centre as maximum sustained wind speed within 44km of the depression centre is about 40 kmph rising to 50 kmph in squalls, it added.

Squally weather may affect the maritime ports, the North Bay, and the adjoining coastal areas of Bangladesh. 

Maritime ports of Chattogram, Cox’s Bazar, Mongla and Payra have been advised to keep hoisted local cautionary signal No 3.

"All fishing boats and trawlers in the North Bay have been advised to take shelter immediately and remain in shelter till further notice," the department said.