The United Nations and other groups urged countries in southern Asia on Friday to rescue as many as 190 people believed to be Rohingya refugees aboard a small boat that has been adrift for several weeks in the Andaman Sea.

Most of those on board are thought to be Rohingya Muslims from Myanmar who had lived in crowded refugee camps in Bangladesh for as many as five years and are seeking a better life in Malaysia and Indonesia.

Messages they reportedly sent by satellite phone to their families describe their situation as desperate.

“Reports indicate those onboard have now remained at sea for a month in dire conditions with insufficient food or water, without any efforts by States in the region to help save human lives,” the UN refugee agency, UNHCR, said in a statement.

“Many are women and children, with reports of up to 20 people dying on the unseaworthy vessel during the journey.”

“All States have a responsibility to rescue those on the boat and allow them to safely disembark in line with legal obligations and in the name of humanity,” it said.

Malaysia and Indonesia both have Muslim majorities, even though groups seeking refuge risk detention on arrival.

The UNHCR said unverified reports indicated the boat is currently north of Aceh in Indonesia.

The journeys are often made this time of year, when seas are usually calmer but remain treacherous, especially because the vessels used by human traffickers are often dilapidated.

Earlier this month, an oil exploration support vessel rescued more than 150 Rohingya after their boat started taking on water and handed them over to Myanmar authorities.

On December 18, the Sri Lanka navy rescued 105 Rohingya refugees whose boat was adrift and sighted by fishermen.

More than 700,000 Rohingya have fled from Buddhist-majority Myanmar to refugee camps in Bangladesh since August 2017, when the Myanmar military launched brutal counterinsurgency operations in response to attacks by a rebel group.

Myanmar's security forces have been accused of mass rapes, killings and the burning of thousands of Rohingya homes.

On Thursday, the UN special rapporteur on the situation of human rights in Myanmar, Tom Andrews, urged governments in South and Southeast Asia "to immediately and urgently coordinate search and rescue for this boat and ensure safe disembarkation of those aboard before any further loss of life occurs.”

“While many in the world are preparing to enjoy a holiday season and ring in a new year, boats bearing desperate Rohingya men, women and young children, are setting off on perilous journeys in unseaworthy vessels,” Andrews said in a statement.

The boat is running out of food and water and its engine has failed, he said.

UNHCR said information on Rohingya boat people is difficult to verify, but if the latest reports are true, they bring "the number of dead and missing in the Bay of Bengal and the Andaman Sea to nearly 200 this year,” or about 10 per cent of the estimated 2,000 people who have taken risky sea journeys in the region during the year.

Chris Lewa, director of the Arakan Project, a private organisation that monitors the Rohingya crisis, said on Thursday her group has collected information received by satellite phone by families of those aboard the boat.

According to the information, Indian authorities at one point provided the drifting ship with food and water but then pushed it in the direction of other countries instead of bringing it ashore, she said in a telephone interview.

Asked about the report, Indian navy spokesperson Commander Vivek Madhwal said Thursday, "?I don't have any inputs on this.”

The messages sent to the families also suggested that a second boat is adrift in the region.