South Africa's top serial killer profilers are to help the Namibian police investigating the murder of four women.

The women - three of whom have been identified as Melanie Janse, 22, Juanita Mabula, 21, and Viola Swartbooi, 18 - are believed to be the victims of a serial killer.

The killer, who has dismembered two of his victims, is thought to have been operating near the capital, Windhoek, since August 2005.

The latest victim, whose identity is unknown, was found dismembered 10 days ago. Her torso, minus her head and arms, was found along with her pelvis, legs missing, in a dustbin at a rest-stop along the B1 highway between Okahandja and Windhoek. The grisly find was made by a motorist dumping rubbish.

A few days later at another rest stop, about 60km away, her thighs were found in a dustbin, police said.

Janse was found naked along the B1 highway. Mabula, who was beheaded, was also found along the B1 close to the Windhoek Turf Club near the Windhoek Country Club Resort in September 2005.

Her head was found in October 2005. It had been left at a roadside between Windhoek and Rehoboth.

Swartbooi was found buried in a shallow grave in Rehoboth in December 2005 after having disappeared from Windhoek.

The B1 is the main Namibian highway, which runs between South Africa and Angola.

Police spokesperson Captain Percy Morokane said that the SAPS Investigative Psychology Unit (IPU) had been assisting the Namibian authorities for the past two weeks.

IPU head Dr Gerard Labu-schagne said he was helping the Namibian authorities to start their investigation. Also, to set up a task team to focus on the investigation, "as serial killing investigations differ from normal murder investigations".

This was the first time that the Namibian police had dealt with a serial killer, he said.

The SAPS were assisting after receiving a request from the Namibian police.

"At this stage Namibian police are following up on a number of leads.

"That country's police have also sent several exhibits to the SAPS Forensic Science Laboratory in Pretoria for examination."

Labuschagne declined to comment on the leads, whether any arrests had been made or what the exhibits were.

The Namibian authorities had requested that the SAPS go back to that country at a later stage to help train its police in serial murder investigations.

He said that the IPU had assisted various countries in solving serial killer cases.

"The latest of these was helping the Central Bureau of Investigation of India with their investigation into the murder of 17 people in the village of Nithari this year.

"The victims were adults and children who had been murdered between 2005 and 2006.

"The killers mutilated some of their victims while they apparently also had sex with some of the bodies," he said.

Labuschagne said the SAPS had assisted the Indian police by providing them with information on how to conduct their investigation.

The SAPS had also helped Swazi police in solving a serial killer case several years ago.

Labuschagne said the SAPS had one of the world's best arrest rates when it came to serial killers.

"This is because South Africa is one of the few countries in the world where our law enforcement agency has a full time Investigative Psychology Unit within the service.

"This allows for far more time to probe and a constant involvement in such investigations," he said.