Malaysian PM Najib Razak has vowed to find those responsible for people-smuggling, after suspected mass graves of migrants were found in the country.

Mr Razak said he was “deeply concerned” by the discovery on Sunday, the first found inside Malaysia.

Police in neighbouring Thailand found human-trafficking camps and dozens of shallow graves earlier in May.

Its subsequent crackdown on trafficking has led to a regional crisis with thousands of migrants stranded at sea.

‘Unburied body’

On Sunday, about 100 bodies believed to be Rohingya migrants were found in mass graves in Malaysia’s northern Perlis state, along the border with Thailand.

The graves were in a restricted area according to a minister in the prime minister’s office Datuk Seri Shahidan Kassim, the Star newspaper reported.

There was a body left unburied at the scene, he said.

“I am deeply concerned with graves found on Malaysian soil, purportedly connected to people-smuggling,” Mr Razak said on his Facebook and Twitter accounts on Monday. “We will find those responsible.”

The graves are evidence of a human trafficking business where migrants are kept in jungle camps while ransom is demanded from family members.

An investigation by the BBC’s Jonathan Head has found entire communities in Thailand helping the traffickers.

Many migrants are believed to have perished from disease or starvation.

The migrants are mainly Rohingya Muslims fleeing persecution in Myanmar where they are not recognised as citizens, but also Bangladeshi economic migrants looking to reach Malaysia through Thailand.

The crackdown in Thailand appears to have caused traffickers to abandon the migrants at sea.

Boats packed with starving migrants were at first being turned away by Indonesian, Malaysian and Thai navies.

Last week, Indonesia and Malaysia agreed to provide temporary shelter to the migrants, but asked for them to be resettled by the international community within a year.