The cyclone lashed the southern Patuakhali coast with wind speed up to 90 kilometres per hour and now proceeded towards northeastern coastlines.
"The cyclone has now touched the land, gradually losing its strength ... It is heading towards Bandarban (hill district) partly ravaging the Noakhali and Chittagong coasts," meteorology department's deputy director Shamsuddin Ahmed told PTI.
The heavy rainfall largely weakened the Mahasen and it was likely to take a natural death once it reached Bandarban hill day after its emergence in the sea, he said, adding that the Storm caused less damage than had been feared as it passed over Bangladesh, sparing Myanmar almost entirely.
Unconfirmed reports claimed six people were killed, but officials said they gathered reports of four deaths in Barguna, Bhola and Patuakhali districts as the Mahasen first struck the southwestern coastline.
The deaths were caused by drowning or the victims were hit by falling trees.
At least 18 deaths were reported in Bangladesh, Myanmar and Sri Lanka, but officials had prepared for a far greater storm as the United Nations had warned that 8.2 million people could face life-threatening conditions.