GEORGE TOWN (THE STAR/ASIA NEWS NETWOR) - Police are now hunting for a fourth suspect believed to be behind the gruesome murder of Myanmar nationals in Penang this year.

Penang police chief Senior Deputy Comm Datuk Wira Abdul Rahim Hanafi said the fourth suspect was believed to be involved in the latest incident at the Metropolitan Park in Relau, where an unidentified person, believed to be a foreigner, was stabbed to death.

"I had said there existed another group of killers and we are tracking down this group of Myanmar nationals.

"The fourth suspect is believed to be involved with this group," he told a press conference at the northeast district police headquarters before launching the crime prevention operation on Sunday.

SDCP Abdul Rahim said the manhunt for the other three suspected killers believed to be from the first group continues.

Police have detained 20 Myanmar nationals including a woman over the past two weeks in an operation codenamed Ops Kelar that was launched to solve the murders.

"Two have been charged under the Immigration Act for not possessing valid travelling documents, six have been released on police bail, while 12 were still detained to facilitate investigation," SDCP Abdul Rahim said.

On Thursday, police said there were two groups of Myanmar nationals involved in the recent spate of grisly murders of their countrymen in the state.