United Nations - The Catholic bishop behind a key political deal in the Democratic Republic of Congo appealed for support at the UN Security Council on Wednesday as a top UN official warned of potential pitfalls for the accord.

The New Year's Eve deal calls for the appointment of a new prime minister and the appointment of a transitional body to pave the way to elections in December 2017 that could bring an end to the rule of President Joseph Kabila.

The agreement was reached after months of violence and could set the stage for the first peaceful transfer of power in the DRC since its independence in 1960.

Archbishop Marcel Utembi told the council that the Congolese people were counting on international backing to turn the deal into reality.

"I ask one thing of the international community," said Utembi, who spoke by video-conference.

"To help the people do everything to ensure the success of this accord, from its implementation to the organisation of presidential and legislative elections according to the agreed timetable."

UN peacekeeping chief Herve Ladsous pointed to potential hurdles, from opposition groups who have yet to sign on to the accord to the reservations expressed by Kabila's party.

Without the full backing of all sides, "the implementation of the accord will be difficult and will have harmful consequences on the political and security aspects," said Ladsous.

Ladsous expressed concern over recent violence in the vast resource-rich country that has been ruled by Kabila since 2001, when he took over from his father Laurent who was assassinated.

At least 40 civilians died in "alleged extrajudicial killings" during clashes on December 19 and 20 between opposition demonstrators and security forces, said Ladsous.

French Ambassador Francois Delattre pointed to a "very positive dynamic, positive momentum" for the agreement but said the council must weigh in.

"I believe it's the responsibility of the Security Council to promote the agreement, with respect to the appointment of the new prime minister, with respect to the definition of a new electoral calendar, and regarding the respect of human rights," Delattre told reporters.

The United Nations has some 20 000 troops in the DRC, its biggest peacekeeping mission.