The wife of a man who died in custody in Malaysia accused officers on Saturday of torturing her husband before beating him to death, in the latest alleged act of police brutality.

Truck driver N. Dhamendran died on May 21 in a police lock-up, 10 days after he was arrested over a fight. His lawyer said he had staple wounds in his ears and "not one inch" of his body was spared from beating.

Police have opened a murder inquiry after a postmorten revealed "criminal elements", and four officers who were questioning the suspect are under investigation. They have been reassigned to desk duty but remain on the force.

Dhamendran's family said the postmortem showed 52 injury marks on his body, including extensive bruising and wounds likely made by a cane and stapler.

Dhamendran's wife M. Marry called on authorities to swiftly charge those involved with murder, which carries the mandatory death penalty upon conviction.

"He didn't even fight back. But look at what they did to him," she said with tears in her eyes. "I want them hanged... I'm ashamed and saddened as a Malaysian citizen."

Two staples were still left in Dhamendran's ear lobes, said N. Surendran, the family's lawyer and an opposition politician.

"This is obviously a form of torture by the police. Not one inch of Dhamendran's body was spared from beating," Surendran told reporters.

"There is adequate evidence to bring murder charges against all police personnel involved."

Allegations of police brutality in Malaysia are frequent, but prosecutions are few.

According to the home ministry, a total of 156 detainees died in custody from 2000 to 2011.

Home Minister Zahid Hamidi said interrogation procedures would be reviewed, including ensuring proper monitoring of suspects' questioning.

"We will re-evaluate the present regulations so that there will not be any similar deaths in the future," he was quoted by The Star newspaper as saying. "Those responsible are individuals, not the entire force."

Last year, a Malaysian court sentenced a constable to three years in jail over the death in custody of another ethnic Indian man, which made headlines in 2009.