A Christian rebel group in Central African Republic ambushed a UN convoy, sparking a firefight that left four peacekeepers dead, the United Nations said on Tuesday.

United Nations: A Christian rebel group in the Central African Republic ambushed a United Nations convoy, sparking a firefight and kidnappings that left four peacekeepers dead, eight injured and one missing, the United Nations said on Tuesday. United Nations spokesman Stephane Dujarric said eight fighters from the anti-Balaka rebel group were also killed in the battle Monday night. The United Nations peacekeeping mission said the remaining attackers fled into the bush.

The United Nations mission sent a helicopter and additional troops to secure the site near Bangassou, about 474 kilometers (295 miles) east of the capital, Bangui, and were continuing to search for the missing peacekeeper, Dujarric said.

In the initial ambush and firefight, one Cambodian peacekeeper was killed and seven Moroccans and one Cambodian were injured, he said.

Three Cambodian soldiers and one Moroccan peacekeeper were also reported missing, according to United Nations and Cambodian officials. Dujarric said three of the missing peacekeepers were later found dead. He said he did not know their nationalities.

The injured peacekeepers were evacuated by helicopter to the capital and are now receiving medical aid, he said, and the United Nations is coordinating with government officials "to ensure the perpetrators are arrested and brought to justice."

United Nations Secretary-General António Guterres issued a statement late on Tuesday strongly condemning the attack and stressing "that attacks against United Nations peacekeepers may constitute a war crime." He urged Central African Republic authorities "to swiftly bring those responsible to justice."

The country descended into sectarian conflict in 2013 when Muslim rebels overthrew the nation's Christian president. The United Nations launched a peacekeeping mission there in 2014 and now has more than 12,000 troops deployed to protect civilians from violence between Christian and Muslim factions.

Some 890,000 people have been displaced inside the country and into neighboring Cameroon, the United Nations says.

The latest fighting began in February and Human Rights Watch said last week that at least 45 people have been killed and 11,000 displaced in attacks by armed groups that have also targeted civilians.

One predominantly Peul faction of the mostly Muslim Seleka group has been fighting since late 2016 with another faction that has aligned itself with the Christian anti-Balaka group as they vie for control of the central part of the country, the rights group said.

Cambodian Prime Minister Hun Sen announced news of the attack in video remarks published on his official Facebook page.

He said the Cambodians were part of an engineering unit that was helping to build roads, bridges and other infrastructure. The ambush took place as the Cambodians were on the way back to their base with an escort of Moroccan soldiers.

Chhum Socheath, a spokesman for the Cambodian National Defense Ministry, said the slain peacekeeper was a captain and his body was being sent home. Cambodia has deployed 12 soldiers to the central African nation in recent months, he said.

Over the weekend, four international aid groups said they would temporarily withdraw their workers from parts of northern Central African Republic because of increasing attacks targeting them. The four Solidarites International, Intersos, Danish Church Aid and Person in Need Relief Mission said they were moving to Bangui.