Peace talks between the government of the Democratic Republic of Congo and M23 rebels were suspended again on Monday even after the United Nations pressed for progress in the troubled negotiations.

Both sides announced a halt in the talks taking place in the Ugandan capital Kampala, just hours after UN envoys warned about the dangers if a deal was not agreed soon to end the year-and-a-half-old rebellion ravaging DR Congo's volatile east.

Congolese government spokesman Lambert Mende said the talks had been suspended because of disagreement over the extent of an amnesty for the M23 army mutineers and their reintegration into the national army.

Mende said Congolese Foreign Minister Raymond Tshibanda had returned home to Kinshasa, but added that his departure was "not definitive".

M23 delegate Roger Lumbala said there was a "blockage" but insisted the rebels were ready to go back to the negotiating table any time.

"We have agreed on the content of 13 articles of a peace accord and two remain to be settled, concerning security measures," M23 delegation chief Rene Abandi told AFP, indicating that measures to take back rebels into the Congolese army were undecided.

Backed by the international community, DR Congo's government is refusing to give amnesty to about 80 leaders of the M23 and to enlist these men into military ranks.

A government official had earlier warned that the negotiations, which resumed in September under pressure from regional leaders, were "heading slowly but surely towards failure".

The UN special envoys issued a statement on Monday voicing concern over the lack of a comprehensive deal for the demobilisation of M23 rebels fighting in the mineral-rich but chronically unstable east.

Scramble for resources

"The envoys are concerned at the volatility in the region and hope that additional progress on the significant remaining issues can be made in the coming days," they said in a statement.

The UN and other special envoys, including from the European Union, the United States and the African Union, jointly urged both sides "to exert maximum restraint on the ground in order for the conclusion of their dialogue".

The M23 consists of ethnic Tutsi fighters from an earlier rebellion who were integrated into the Congolese army under a peace pact in 2009, then mutinied in April 2012 and turned their guns on their fellow soldiers, accusing the government of failing to keep the deal.

The rebels control an area of around 700 square kilometres (270 square miles) in the eastern North Kivu province, which borders Rwanda and Uganda.

On November 20 last year, M23 forces seized the key provincial capital of Goma, a city of one million people, but withdrew in early in December under international pressure.

The hotbed region was a primary battleground in successive wars between 1996 and 2003 as rival armies scrambled for control of its rich mineral resources, including gold and coltan, which is a prized component of electronic technology such as mobile phones.

Since a 2003 peace agreement, both North and South Kivu provinces have remained highly unstable because a multitude of rebel movements, tribal militias, army deserters and military units are fighting for control of territory and resources.

The United Nations and Kinshasa regularly accuse Rwanda and Uganda of supporting M23, something both countries deny. Monday's UN statement commended "good faith efforts" by the Kinshasa government to reach a peace deal.

A heavily armed 3,000-strong UN intervention brigade has deployed in DR Congo -- alongside 17,000 UN peacekeepers already in place -- with a mission to carry out offensive operations against the rebel fighters, who are accused of human rights abuses including rape, murder and recruiting child soldiers.