Malaysian authorities' move to go public with the personal details of a Bangladeshi migrant worker, who is wanted by them for speaking up on alleged mistreatment by immigration officers, has sparked criticism from rights activists.

The criticisms came following a fresh round of xenophobic and anti-migrant comments on Malaysia's immigration department's Facebook page, reports Free Malaysia Today.

Many social media users even advocated violence against Md Rayhan Kabir, a migrant who was interviewed in a documentary produced by Al Jazeera.

"If you see him, slap him once or twice," wrote Facebook user Hertonnye Linggom, in response to a mugshot of Rayhan posted on the immigration department's Facebook page.

"Let us Malaysians together help to locate him. It won't take long to succeed. Don't forget, use a wire, not a rope, to tie him," said another user, Ku Lim Ku.

Rayhan (25) attracted the authorities' attention after he appeared on an episode of Al Jazeera's 101 East programme on the alleged mistreatment of migrants during the recent lockdown.

Activists said Rayhan could now be a target of reprisal attacks despite having committed no crime warranting a nationwide witch-hunt.

Bangkok-based John Quinley of human rights group Fortify Rights said Rayhan had only spoken up about the problems many migrants and refugees face in immigration detention centres.

"The Malaysian government should not target individuals who speak to the media about the vulnerabilities migrants face in the country," Quinley told Free Malaysia Today.

"Instead of intimidating migrants, the government should protect them," Quinley added.

On Tuesday, pictures of Rayhan were splashed on several news websites alongside the details of his Bangladeshi passport which were released to the media by the immigration department.

Authorities said Rayhan was wanted in an investigation under the Immigration Act 1959/63.

Echoing Quinley, local rights activist Muhammad Afiq Noor said the "wanted" notice for Rayhan was uncalled for.

"The concerns he raised in the documentary are legitimate and not without basis," he added.

He said claims in the documentary were nothing new, and had been raised by the government's rights commission Suhakam.

"As a nation, we have a legal and religious responsibility to treat migrants with dignity and uphold their basic rights, including freedom of speech," Afiq told FMT.

"If the immigration finds something incorrect in the documentary, just issue a statement refuting it.

"The intimidation against the press and the vulnerable migrants is unnecessary and a threat to our democracy," he said.

Afiq, who was trained as a lawyer, however said the immigration was legally mandated to initiate investigations into offences that fall within its jurisdiction, including divulging personal details.

But he said Rayhan's offence was unclear.

"If it is related to his criticism in the documentary, then it is not an offence under the Immigration Act.

"Why didn't they specify the provision, and under which section of the law he was being investigated for? And why specifically this one man? Is it because he appeared in the documentary and criticised how we handled immigrants during MCO?" he asked.

He said if Rayhan's offence was staying in the country illegally, putting up posters of him was inappropriate as it could spur xenophobia.

"I think the real concern is that the immigration department appears to be attempting to silence criticism. The action (of issuing the notice) is not necessary."