KIGALI, Rwanda (AP) _ Six Hutu rebels have been charged in the 1997 killings of four U.N. human rights monitors, state-run Rwandan radio reported Saturday.

The monitors and their driver were ambushed near Cyangugu, 150 miles southwest of Kigali and on the border with Congo, where the rebels cross easily in and out of the country.

U.N. human rights spokesman Jose-Luis Herrero said the six accused were captured in Cyangugu in February 1997. He had no other details.

The six _ five men and a woman _ had been charged with involvement in the killing, armed robbery and state security.

The court in Cyangugu agreed Friday to adjourn proceedings until April 16 because the accused did not have lawyers and had not been told of their right to have them, Herrero said. They did not enter pleas, he said.

The killing has severely restricted the movement of U.N. rights monitors and made it difficult for them to gather reports on human rights violations outside Kigali.

Thousands of people have been killed in rebel attacks and army reprisals since the return in November 1996 of more than 1 million Hutu refugees from exile.

Authorities say former Hutu soldiers and militiamen, responsible for the 1994 Hutu-organized genocide of 500,000 minority Tutsis, mixed in along with refugees and are bent on destabilizing the country.