Malaysian authorities have found mass graves containing the remains of more than 20 people believed to be human trafficking victims near the country's border with Thailand, police said on Sunday.

The 24 remains, believed to be of Rohingya and Bangladeshis, were recovered from 19 graves found at bordering Wang Burma hill area, Malaysian newspaper The Star reported.

Reuters news agency however reported that it was not immediately clear if the bodies discovered were those of Rohingya, a minority ethnic group in Myanmar, whose members have fled widespread persecution in that country.

They were suspected to have died of abuse or malnourishment.

The heavily forested Thai-Malay border has been a transit point for smugglers bringing people to Southeast Asia by boat from Myanmar and Bangladesh.

The migrants are often held for ransom in squalid detention camps and according to some accounts face torture and starvation.

Police uncovered 24 bodies on Saturday in the Bukit Wang Burma area near the Malaysian border with Thailand, close to where authorities in May had found hundreds of bodies in illegal detention camps.

"Following on from the operation in which we found ... bodies of illegal immigrants, 24 more bodies have been found and dug up," police said in a statement, adding that the remains had been handed over to medical experts.

National Security Council chairman Shahidan Kassim confirmed the discovery.

"It was raining heavily recently and the downpour swept away the soil and revealed the remains."

"We don't know how long the victims were buried or if there was a transit camp there," he said.

The remains have been sent to Sultanah Bahiyah Hospital in Alor Setar, Kedah, for a post-mortem.

A crackdown by Thai authorities in May drove traffickers to abandon thousands of migrants on rickety, overcrowded boats in Southeast Asian waters, triggering a regional humanitarian crisis that saw them land in Malaysia and Indonesia after being rescued by fishermen.

In Ops Wawasan Khas, operation to exhume bodies of human trafficking victims which was conducted from May 11 to May 23, police found 139 graves scattered around 28 transit camps abandoned by a human trafficking syndicate in Wang Burma hill and Wang Perah hill.

The skeletal remains of 106 victims were found and have been buried in a mass grave in Kampung Tualang, Pokok Sena, near Alor Setar.