Myanmar immigration authorities detained more than 100 suspected Rohingya on board a boat off Yangon, officials said, raising fears of a fresh wave of dangerous voyages after a 2015 crackdown on people smugglers.

The boat carrying 106 people was stopped some 30 km south of Myanmar's largest city and senior police officials were on the way to investigate them, Kyaw Htay, an immigration officer from the Kyauktan township, told Reuters news agency.

"It's possible that they are from Rakhine. Like in previous years, it is possible they are Bengali from Rakhine," Kyaw Htay was quoted as saying by Reuters.

Many people in Myanmar refer to the Rohingya as "Bengali", implying they are illegal immigrants from Bangladesh.

More than 700,000 Rohingya fled a sweeping army crackdown in Myanmar's Rakhine state last year, according to United Nations agencies.

The Rohingya said soldiers and local Buddhists massacred families, burned hundreds of villages, and carried out gang rapes.

UN-mandated investigators have accused the Myanmar army of "genocidal intent" and ethnic cleansing.

Myanmar has denied almost all of the allegations, saying security forces were battling "terrorists".

Attacks by Rohingya armed groups calling themselves the Arakan Rohingya Salvation Army preceded the crackdown.

Officials and aid workers told Reuters last week that dozens of Rohingya in Myanmar and Bangladesh had boarded boats to try to reach Malaysia in recent weeks, after the end of the monsoon rains in early October.

Observers warn that because the smuggling routes to Thailand have been disrupted and the journey is treacherous and expensive, more and more Rohingya are opting for a cheaper and shorter trip along the Bay of Bengal coast south to Yangon.

Aye Mya Mya Myo, a lower house lawmaker for Aung San Suu Kyi's ruling National League for Democracy (NLD) party from Kyauktan, posted pictures of a rickety boat crammed with women wearing headscarves, men and children on Facebook.

On some images police officials kept watch over squatting people from the boat.

She said there were 50 men, 31 women and 25 children on the boat.

It resembled vessels the Rohingya typically use to escape the apartheid-like conditions in Rakhine, where they are denied free movement and access to decent education and healthcare.

For years, Rohingya on both sides of the border have boarded boats organised by smugglers in the dry months between November and March, when the sea is calm. The perilous journey to Thailand and Malaysia, often undertaken in overcrowded vessels, has cost many lives.

Thailand cracked down on the trade after discovering a series of mass graves in 2015, leading to a crisis when smugglers abandoned their human cargo and left boats adrift in the Andaman Sea.

Meanwhile, Myanmar's neighbouring country, Indonesia, said it is ready to help resolve the Rohingya crisis. 

"Indonesia is ready...to help the Myanmar government to create a conducive condition in the Rakhine State, where freedom of movement should be respected," Indonesian President Joko Widodo was quoted by the country's Antara news agency as saying, at the sidelines of a regional summit in Singapore on Friday.