The United Nations called Saturday for the urgent rescue of 185 people, mainly women and children, on a distressed boat last heard to be near the Andaman and Nicobar Islands in the Indian Ocean.

Around 70 of those onboard are children and 88 are women, the UNHCR refugee agency said in a statement.

"At least a dozen are feared to be in critical condition with one individual reported to have already died," it said.

"Many more could die under the watch of numerous coastal states without timely rescue and disembarkation to the nearest place of safety."

UNHCR spokesman Babar Baloch told AFP the agency was reaching out to all the coastal authorities in the area to rescue the migrants, who are believed to be Rohingya.

"It is really a desperate situation," he said.

Thousands of the mostly Muslim Rohingya, heavily persecuted in Myanmar, undertake risky sea journeys from Myanmar and refugee camps in Bangladesh every year trying to reach Malaysia or Indonesia.

More than 2,000 Rohingya are believed to have attempted the risky journey to Southeast Asian countries in 2022, according to UNHCR.

And since last year, more than 570 people, including Rohingya refugees, have been reported dead or missing at sea in the region, it said.

When it comes to the people currently adrift, the agency emphasised that "a bigger tragedy is preventable with timely efforts to save lives".

"This situation once again underlines the importance of all states in the region deploying their full search and rescue capacities to avoid human disasters happening at this scale."