At least 20 Rohingya have died at sea in recent weeks, the UN refugee agency (UNHCR) said on Tuesday, as boats carrying hundreds of the persecuted Muslims landed in Indonesia while others were believed to be adrift in the Indian Ocean.

A boat washed ashore in Indonesia's Aceh province on Monday carrying 174 Rohingya, most of them dehydrated, fatigued and in need of urgent medical care after weeks at sea, local disaster agency officials said.

Chris Lewa of the Arakan Project, which provides support to Rohingya, said the boat was the same as one earlier reported missing and feared to have sank.

The UNHCR on Monday said 2022 could be one of the deadliest years at sea in almost a decade for the Rohingya, as a growing number of them flee desperate conditions in refugee camps in Bangladesh.

The Rohingya have long been persecuted in Buddhist-majority Myanmar, which borders Bangladesh. For years many have fled to countries like Thailand, and Muslim-majority Malaysia and Indonesia between November and April when seas are calmer.

Nearly 1 million live in crowded conditions in Bangladesh, including many of the hundreds of thousands who fled a deadly crackdown by Myanmar's military in 2017.

Rights groups have recorded a significant increase in the number leaving the camps, from about 500 last year to an estimated 2,400 this year. It is not clear what is driving the larger exodus. Some activists believe the lifting of COVID restrictions around Southeast Asia, a favoured destination for the Rohingya, could be a factor.

"We came here from the largest Bangladesh refugee camp with the hope that the Indonesian people would give us the opportunity of education,” said Umar Farukh, who spoke in a shelter crowded with Rohingya men, women and children receiving care from Indonesian medics.

The group is the latest in a series of boat landings and rescues around the region in recent weeks.

There were 57 other Rohingya who reached Aceh on Sunday, while two other boats carrying a combined 230 people landed in November.

Earlier this month, Sri Lanka's navy rescued 104 Rohingya, while Thai authorities saved six others who were found clinging to a floating water tank.