Four Thai citizens were extradited to Malaysia on Thursday where they will face trial over mass graves linked to human trafficking, Malaysia's home minister said.

Over a hundred bodies were discovered in 2015 buried deep in the Malaysian jungle along the border with Thailand, triggering an investigation into human smuggling in the Southeast Asian nation.

The region has long been a gateway for persecuted Rohingya Muslims fleeing violence in their native Myanmar and economic migrants from Bangladesh.

Smugglers in previous years have brought tens of thousands of Rohingya on a perilous journey over land and sea to Malaysia, a relatively affluent and safe Muslim-majority country.

Home affairs minister Saifuddin Nasution said Malaysia in 2017 has asked Thailand to extradite 10 of its citizens believed to be linked to the case.

"As a result of the good cooperation between the two countries, four out of 10 individuals have been successfully tracked down," Saifuddin said in a statement.

He said a Thai court issued an arrest order in March this year for the four suspects to be handed over to Malaysia before they were extradited on Thursday.

The four unnamed individuals will face unspecified charges in a court in Malaysia's northern Perlis state starting Friday.

A 2019 report by Malaysian human rights commissioners and a rights group said a human smuggling syndicate operated in the area from 2012 to 2015.

Migrants were reportedly held in inhumane jungle camps where they faced physical violence and were often denied adequate access to food and water.

AFP