49 fishermen have been rescued since Saturday, the officials said. (Representational)

Six of the 31 fishermen, who had gone missing in the Bay of Bengal after venturing into deep waters despite weather warnings four days ago, were rescued on Monday but 25 are still missing, officials said.

Thirteen other fishermen on another boat, which had developed a snag and drifted into the Bangladesh waters due to inclement weather, were rescued by the coast guards of India and the neighbouring country in a coordinated operation on Saturday, a Defence official had said.

With this, 49 fishermen have been rescued since Saturday, the officials said.

The secretary of the fishermen's association at Kakdwip, Nikon Maity, said six fishermen of FB Dashabhuja were rescued by fishermen in Haribhanga islet of Bangladesh and they were brought to Kakdwip on Monday morning.

The missing fishermen had started from Namkhana in South 24 Parganas district of West Bengal on four trawlers - FB Nayan, FB Dashabhuja, FB Babaji and FB Joy Jogiraj - on Thursday, Maity said.

Though FB Dashabhuja, FB Joyjogiraj and FB Babaji are feared to be submerged, 15 fishermen each from FB Joyjogiraj and FB Babaji have been rescued.

The whereabouts of FB Nayan with 16 fishermen on board are still unknown. Nine fishermen from FB Dashabhuja are also missing, Maity said.

After getting information about the missing fishermen by the West Bengal Fishermen Association, Sundarban Development Minister Manturam Pakhira had asked the South 24 Parganas district authorities to launch a search and rescue operation.

All the missing fishermen were from Kakdwip area.

The Indian Coast Guard (ICG) and its Bangladesh counterpart had rescued 13 crew members on board an Indian fishing boat amidst very rough sea conditions and inclement weather, the Defence official said Sunday.

The 13 crew members of fishing boat ''FB Tara Shankar'', which had ventured to the Bay of Bengal from Kakdwip, were rescued on Saturday amidst very rough sea conditions and inclement weather, the official said.

The boat had developed a technical problem and on receiving the information, the ICG regional headquarters contacted the Bangladesh Coast Guard (BCG) West Zone headquarter at Mongla.

A Bangladesh Navy ship located the Indian boat with 13 crew on board near the Mongla Fairway Buoy in the evening on Saturday and rescued all the crew members on the boat.

The Bangladesh Naval ship took the Indian disabled boat under tow and brought it to Pussur river mouth, which is approximately 60 nautical miles eastward of the Indo- Bangladesh maritime border, where 100 more Indian fishing boats were sighted.

The disabled boat was handed over to one of the operational Indian boats for towing back to India.

As the sea was rough, around 100 Indian fishing boats, including the disabled one under tow, were guided by the Bangladesh Naval ship for taking passage through the riverine/coastal route westward up to the Haribhanga river, the official said.

The coast guards of India and Bangladesh have a memorandum of understanding (MoU) followed by a ''Standard Operating Procedure'' for helping each other during such incidents and making waters of north Bay of Bengal safe, he added.