Feb 22 (Reuters) - A month-old peace accord in eastern Democratic Republic of Congo faced a new problem on Friday when Tutsi rebels halted participation in a ceasefire commission to protest U.N. allegations they had massacred civilians.

The move announced by renegade Tutsi General Laurent Nkunda posed a threat to the Jan. 23 ceasefire and peace pact signed by the government, Nkunda's rebels and rival local militia groups.

The U.N. and Western governments brokered the deal hoping for a lasting peace in turbulent eastern Congo, where violence has persisted long after the formal end of a 1998-2003 war in the central African state.

Here are some details of the conflict in the east.

* ORIGINS OF THE CONFLICT:

-- The roots of Nkunda's rebellion in North Kivu lie in unhealed ethnic and political tensions that make the racially mixed eastern Congo a regional tinderbox.

-- The presence in east Congo of both Tutsi and Hutu rebels stems from Rwanda's 1994 genocide, in which 800,000 Tutsis and moderate Hutus were killed in 100 days by the Hutu-led government and ethnic militias.

-- The Hutu presence led to invasions by Rwandan forces that helped ignite a wider war in Congo from 1998 to 2003, in which some 4 million people died, most of hunger and illness.

-- Nkunda led a revolt in 2004 with 4,000 soldiers and briefly captured Bukavu, capital of South Kivu. He was the subject of an international arrest warrant for war crimes committed during the Bukavu occupation, but Congolese officials say this warrant has since expired.

-- After 2006 elections aimed at drawing a line under the 1998-2003 war, Congolese President Joseph Kabila promised to bring peace to east Congo.

-- In November 2006, U.N. Mission in Congo (MONUC) helicopters and armoured vehicles killed hundreds of Nkunda's fighters in fierce clashes.

-- Under a January 2007 peace deal, Nkunda's fighters joined special mixed army brigades, but walked out again in August.

-- Nkunda says he is fighting to protect his Tutsi people in eastern Congo against attacks by the rebel Democratic Forces for the Liberation of Rwanda (FDLR) which controls parts of North Kivu. He says the FDLR Rwandan Hutu rebels are backed by Kabila's government, a charge the government denies.

-- The FDLR includes former Rwandan soldiers and members of Hutu militias, or Interahamwe, which took part in the Rwandan genocide.

* CEASEFIRES:

-- U.N. mediators announced a limited ceasefire on Sept. 6, 2007 after nearly two weeks of fighting in North Kivu province in which thousands of Nkunda's Tutsi fighters appeared to have turned the tide on government forces and were pressing ahead towards the provincial capital Goma.

-- Nkunda, who had turned parts of North Kivu province into his personal fiefdom, later said he was abandoning the ceasefire because of attacks by the government, which in turn accused him of pushing the country towards war.

-- Fresh talks opened in January 2008 at a peace conference in Goma, grouping government officials, local leaders and the warring factions.

A peace pact signed on Jan. 23 included a ceasefire to the conflict that has displaced more than 400,000 people in North Kivu in the past year.

-- Nkunda suspended his group's participation in the ceasefire commission on Friday after U.N. investigators alleged that his fighters killed at least 30 Hutu civilians last month while his rebel group negotiated the peace deal. He called for an independent inquiry into the allegations. (Writing by David Cutler, London Editorial Reference Unit; Editing by Pascal Fletcher)

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