Congo's opposition coalition picked businessman and lawmaker Martin Fayulu to be its candidate in a December presidential election, it said in a statement.

Fayulu will face President Joseph Kabila's preferred successor for the ruling party, Emmanuel Ramazani Shadari, in Democratic Republic of Congo's election on December 23.

In power since his father died in 2001, Kabila and the ruling party are unpopular across Congo, especially in the west and the capital Kinshasa, but a weak and divided opposition has so far failed to capitalise on the Congolese' resentments.

Picking a unified candidate at least gives the opposition someone to rally around.

Kabila surprised a lot of Congolese when he agreed to step aside in August, which would make December's election, if it goes ahead, Congo's first peaceful change of power since independence from Belgium in 1960.

An opinion poll in July, before Kabila came out to back Ramazani, showed opposition leaders were favoured by about 70 percent of voters, but the ruling party enjoys significant financial and institutional advantages.

Several prominent opposition leaders, including former vice president Jean-Pierre Bemba and millionaire businessman Moise Katumbi, were barred by authorities from running, decisions the opposition accused of being politically motivated.