Early on Monday, fighting broke out around two villages in Democratic Republic of Congo's east North Kivu province between rebels loyal to renegade General Laurent Nkunda and the Pareco Mai Mai faction. Both sides blamed each other for attacking.

The clashes near Lusirandaka and Kasake, around 70 km (44 miles) west of Goma, raised fears of a breakdown of a ceasefire and peace deal signed last week by Congo's government with 25 armed groups, including Nkunda's rebels and the Pareco faction.

But spokesmen for Nkunda and the Pareco group said they would stand by the peace accord, which aims to end years of conflict that has raged on in Congo's turbulent east despite the formal end of a wider 1998-2003 war in the country.

Continued fighting has added to a humanitarian catastrophe that has caused more deaths -- 5.4 million since 1998 -- than any other conflict since World War Two, relief experts say.

"This does not endanger our commitment, but the violations of the ceasefire by Pareco worry us," Seraphin Mirindi, a military spokesman for Nkunda, told Reuters. The area where Monday's clashes took place was calm on Tuesday.

"We signed and we respect what we signed. We will not pull out of the process," said Pareco spokesman Theophile Museveni.

The United Nations mission in Congo, whose peacekeepers are setting up buffer zones in North Kivu as part of the ceasefire deal, said it was cautiously optimistic the peace accord could be successfully implemented despite Monday's violence.

"The deal has been signed only recently. In an area with difficult terrain, with a large number of heavily armed people who don't necessarily love each other, there is bound to be friction," U.N. mission spokesman Kemal Saiki said.

"I don't think trust will be established overnight, and for a ceasefire to work, you need a modicum of trust," he added.

Nkunda's spokesman Mirindi said the Congolese army was respecting the ceasefire in North Kivu, where fighting over the last year between government forces, Nkunda's rebels and Mai Mai militia has driven 400,000 civilians from their homes.

President Joseph Kabila, who won elections last year in the vast, former Belgian colony, has vowed to pacify the east.

Although Wednesday's accord raised peace hopes, analysts warned its implementation, including the creation of a military commission to monitor the ceasefire and an amnesty to be offered to rebel and militia fighters, could still create problems.