Two mass graves have been discovered in Kenya's coastal Tana Delta region, the number and identities of the bodies in the graves are unknown, police say.

The discovery of the graves comes a week after at least 38 people were shot, hacked and burnt to death after two tribes fought over land and water in the same area.

The graves were located in Kilelengwani village, the epicentre of fighting that has left 100 people dead in the last three weeks, including nine police officers.

The scale of the recent unrest has left many Kenyans convinced it was politically instigated and has raised fears of serious tribal fighting before elections next March.

A court order to exhume the bodies was requested on Tuesday.

"We don't know yet whether they are attackers who died while in confrontation with security personnel, or were just victims killed by attackers during the clashes and buried," regional police chief Aggrey Adoli said.

Curfew

President Mwai Kibaki imposed a curfew last week and sent extra security forces to the area to try to end the violence, intensified by an influx of weapons in the last few years.

Settled Pokomo farmers and semi-nomadic Orma tribesmen have clashed for years over access to grazing, farmland and water in the coastal region.

Dams along the Tana River, Kenya's longest, supply about two thirds of the country's electricity.

The violence follows warnings last month by the Red Cross that more than 200 Kenyans have been killed in ethnic clashes since January.

The latest pattern of violence has conjured up the spectre of the large-scale ethnic violence that erupted in the aftermath of disputed 2007 polls.