A day of killing 12 people after barrelling in from the Bay of Bengal with wind speeds up to 185 kmph, severe cyclonic storm Amphan on Thursday weakened and lay centered over Bangladesh about 270 north-northeastwards of Kolkata with a wind speed of 27 kmph.

The super cyclonic storm Amphan (pronounced as UM-PUN) moved "north-northeastwards with a speed of 27 kmph during the past six hours, further weakened into a cyclonic storm and lay centered at 5.30 a.m. on Thursday over Bangladesh near latitude 24.7 degrees N and Longitude 89.5 degrees E about 270 km north-northeast of Kolkata, 150 km south of Dhubri and 110 km south-southeast of Rangpur (Bangladesh)", the India Meteorological Department (IMD) said.

"It is very likely to continue to move north-northeastwards and weaken further into a deep depression during the next three hours and into a depression during subsequent six hours," the IMD said.

It said that the Cyclone is now centred over Bangladesh and it will have no adverse impact over West Bengal and Odisha -- a good sign as it cut a swathe through northern Odisha before bearing down on West Bengal where it claimed 10-12 lives, flattened houses and cast aside trees and electricity poles like matchsticks in six-and-a-half hours of monstrous fury that left Kolkata and most of south Bengal pulverised.

While Odisha was spared the worst of Amphan, the Suderbans region and six south Bengal districts felt the full impact of winds gusting at 155-165 kmph along with torrential rain after the cyclone made landfall near Sagar Island around 2.30 p.m. on Wednesday and entered Kolkata, about a 100 km north, around 5 p.m.

Amphan, a Thai name that means sky, is the most severe storm in the Bay of Bengal since the Odisha super cyclone of 1999.

  Cyclone Amphan has lost its intensity and turned into a land deep depression, Bangladesh Meteorological Department said in its latest bulletin.

The cyclone will weaken gradually by giving precipitation. The Met Office instructed the maritime ports to lower great danger signals and hoist local cautionary signal No. 3 instead, said Shamsuddin Ahmed, director of the weather office.

On Wednesday, the maritime ports of Mongla and Payra were advised to keep following great danger signal No. 10, while Chattogram and Cox’s Bazar ports were advised to continue hoisting great danger signal No. 9, as Amphan approached the coast.

The low lying areas of the coastal districts and their offshore islands and chars were inundated by storm surges of 10-15 feet above the normal astronomical tide.

The cyclone killed at least 16 people in Bangladesh and India, destroyed thousands of homes and flooded low-lying coastal areas as it cut a merciless path through the two countries.

In Bangladesh, at least six people were reported dead in Patuakhali, Satkhira, Pirojpur, Bhola and Barguna, bdnews24 reported.