Rwanda's army accused of killing civilians after mass grave of hundreds is uncovered in Congo

United Nations soldiers believe they have uncovered mass graves in the Democratic Republic of Congo (DRC), where hundreds of civilians executed by Rwandan soldiers were buried.

The discovery threatens to destroy Rwanda's image as a country that recovered from genocide to become one of east Africa's most benign and stable regimes.

The graves contain bodies thought to belong to Rwandan Hutu refugees and villagers killed by the Tutsi-led Rwandan army and the Alliance of Democratic Forces for the Liberation of Congo Zaire (AFDL), a Congolese rebel group, in 1996.

The soldiers discovered the grave near Rutshuru, 50 miles north of Goma in the east, while they were digging for latrines. After the first bodies were found, villagers led the UN soldiers to more graves filled with bones. At one, they said 300 people had been killed by machete strikes or a bullet.

The Rwandan army entered the DRC in the mid-1990s under the pretext of hunting Hutu extremists who massacred some 800,000 Tutsis and moderate Hutus during the 1994 genocide. They weresupported by the AFDL, which ousted the late Zairean dictator Mobutu Sese Seku in 1997 and installed their leader, Laurent Kabila, as president.

Thousands of Rwandan Hutus fled to Congo in 1994, fearing reprisals from the new, post-genocide Tutsi-led government. Human rights groups have long believed that these refugees and local villagers were killed and raped by the Rwandan army and Congolese rebel groups in the mid-1990s. The local population has so far been too afraid of reprisals to speak.

Jacqueline Chenard, the UN spokesman, said: "The population is speaking more openly now ... Hundreds of people were rounded up and executed during this period. The local population said that the people in the graves were Rwandan Hutus and members of the local population killed by the AFDL ... in October 1996. They said the soldiers called meetings and at the meetings people were killed by machetes so there was less noise.''

A UN human rights team tried to investigate claims that Kabila's troops had massacred Rwandan Hutu refugees in 1997 but government officials refused to let the team into the DRC, accusing the special UN investigator, Roberto Garreton, of pursuing an agenda that was "full of lies." Mr Garreton has since accused the Congolese government and the Rwandan army of violating human rights.

The Rwandan government, which came to power in 1994 after overthrowing the genocidal Hutu regime, has enjoyed good relations with the West, despite its dictatorial style of government and invasion of the DRC. Britain is Rwanda's biggest aid donor: in 2004-05, it provided £46m in aid.

These mass graves, the largest of their kind so far found in the region, are expected to provide evidence of the atrocities carried out by the Rwandan army and put international pressure on the Rwandan and Congolese governments to investigate the killings.

Mr Kabila later fell out with Rwanda over its involvement in the mineral righ eastern Congo. The fall-out dragged the DRC into another uprising in 1998 that sparked a five-year civil war that drew in six neighbouring countries and claimed four million lives.

A tentative peace process has been established in the DRC and elections are to be held next year, but fighting has continued in the east, and the country still has tense relations with its neighbours. On Monday, the DRC's ambassador to the UN warned Uganda's President, Yoweri Museveni, not to send troops in to attack the Lord's Resistance Army, a Ugandan rebel group.

A history of violence

* 1971 Joseph Mobutu renames the country Zaire, and himself Mobutu Sese Seko.

* 1996-97Rwandan-backed Tutsi rebels capture much of east Zaire while Mobutu is abroad for medical treatment.

* 1997 May Tutsi and anti-Mobutu rebels, aided by Rwanda, capture the capital, Kinshasa; Zaire is renamed the Democratic Republic of Congo; Laurent-Desire Kabila installed as president.

* 1998 August Rebels backed by Rwanda and Uganda rise against Kabila.

* 2000 UN Security Council authorises a 5,500-strong UN force to monitor ceasefire but fighting continues.

* 2001 January President Laurent Kabila is shot dead. Joseph succeeds his father.

* 2001 February Rwanda, Uganda and the rebels agree to a UN pull-out plan.

* 2001 May US refugee agency says the war has killed 2.5 million people. The UN says the warring parties are plunderinng gold, diamonds, timber and coltan.

* 2002 July DRC and Rwanda sign a peace deal: Rwanda will withdraw and DRC will arrest Rwandan Hutus blamed for the 1994 genocide.