An ambush killed a Moroccan peacekeeper and wounded three others on Sunday in the Central African Republic, the United Nations said, blaming pro-Christian armed groups for the violence.

"A MINUSCA (peacekeeping mission) military convoy was targeted by Anti-balaka," it said of the clash in the southern city of Bangassou.

The country is struggling to emerge from a civil war that erupted in 2013 following the overthrow of former President Francois Bozize, a Christian, by Muslim rebels from the Seleka coalition.

The coup led to the formation of "Anti-balaka" vigilante units, drawn from the Christian majority, which began to target Muslims. Both sides committed widespread atrocities.

OPINION: World's most neglected conflict rages on in the CAR

"The attack took place while the Moroccan peacekeepers were escorting water tankers to the river to help resupply the village," the MINUSCA force said on Sunday, condemning the assault and sending "condolences to the family, the people and the government of Morocco".

Earlier on Sunday, the UN condemned an "attack by Anti-balaka near a cathedral where a number of displaced people are living". Two children were seriously wounded, it said.

On Friday, a patrol of peacekeepers was shot and one of the attackers killed, Herve Verhoosel, spokesman for MINUSCA, told AFP news agency on Saturday, blaming pro-Christian armed groups once again.

On the same day, a Muslim woman was kidnapped by what is believed to be an Anti-balaka unit and six Christians were held by Muslims. All were released on Saturday following negotiations.

Six peacekeepers were killed in May in the city and surrounding region, which lies around 470km from Bangui on the border with the Democratic Republic of Congo.

Armed groups are still flourishing given the weakness of the state.

Former colonial power France intervened in 2013 to stop violent Christian-Muslim clashes and formally ended its peacekeeping mission only last month, hailing it a success despite fresh outbreaks of violence.

That leaves mainly the UN's 12,500-strong MINUSCA peacekeeping mission to protect civilians from armed groups.