KINSHASA, Congo -- The United Nations said Friday its investigators have discovered three mass graves at a northeast Congo military camp containing the bodies of 30 people -- including women and children -- who were allegedly killed by soldiers.

The dead were found at the camp in eastern Ituri province after witnesses accused troops of killing dozens of people two months ago, U.N. spokesman Kemal Saiki said.

Saiki said the graves had been opened and the bodies would be exhumed for a team of investigators that includes U.N. human rights officials and Congolese military authorities.

It was not immediately clear what sparked the killings.

Much of Ituri province, home to dozens of powerful local militia groups, has remained lawless and violent despite peace deals to end Congo's 1998-2002 civil war. Tens of thousands of people have died as a reults of the fighting there in the last decade.

Congo's army has been accused by rights groups and residents of rape, pillaging and forcing civilians into labor.

The government is struggling to rebuild the postwar force into a unified military composed of rebels, militias and soldiers who fought each other for years.

The discovery of the graves came at a time of increased tension in Congo over the results of last month's presidential runoff.

Interim President Joseph Kabila was declared the winner, receiving 58 percent of the vote, compared with nearly 42 percent for former rebel leader Jean-Pierre Bemba, who alleged the election was tainted by fraud.

A hearing on vote fraud charges has been delayed after part of Congo's supreme court was burned Tuesday amid gunfire and street fighting among Bemba's supporters.

Fighters loyal to Bemba were leaving the capital Friday after the government ordered his troops to return to barracks outside the city, officials and witnesses said.

A convoy of trucks filled with dozens of fighters could be seen rolling out of Kinshasa toward the nearby town of Maluku. Bemba's fighters first began leaving Thursday.

Kabila's government issued the order to leave earlier this week.

Bemba, whose forces have clashed in Kinshasa twice with those of Kabila in election related violence, has hundreds of fighters here, many serving as his personal bodyguards.