"A majority of the cases relate to (ethnic minority) Tamils," probe chairman Mahanama Tillakaratne said.

"Locally and internationally there has been a big issue of abductions, disappearances and unsolved killings," he said. "This is something very bad for the image of the country."

Tillakaratne was named last year by Sri Lankan President Mahinda Rajapakse to investigate a wave of killings and disappearances that has shaken the country where Tamils are fighting for an independent homeland.

Many of the victims have been executed with their hands tied behind their backs and shot through the head.

During the same September to February period, a total of 2,020 people were either abducted or disappeared, Tillakaratne added.

Some 1,134 were later found alive and reunited with their families.

The fate of the remainder is unknown, Tillakaratne said.

"The cases are so complicated that even if you get Scotland Yard (detectives) you may not be able to solve them," he said.

Sri Lanka is facing mounting criticism over its inability to stem the wave of killings and abductions which have risen with the escalation of fighting between troops and Tamil Tiger rebels in the island's northeast.

On Wednesday, Japan, the single largest donor to Sri Lanka, voiced concern about the human rights situation in the island nation during a visit by Colombo's foreign minister.

A Norwegian-brokered 2002 truce began unravelling in December 2005. Since then, more than 5,000 people have been killed in fighting across the north and tsunami-ravaged east of the country.

The 35-year-old conflict has left at least 60,000 people dead.