UNITED NATIONS — Mainly Christian anti-Balaka forces attacked a U.N. police checkpoint in Central African Republic on Monday, killing one U.N. peacekeeper and wounding three others, the United Nations said.

The attack took place at the entrance to a camp for displaced people in the southeastern town of Bria after peacekeepers intervened to free two displaced people being held hostage by anti-Balaka forces, U.N. spokesman Stephane Dujarric said.

He said the peacekeeper who died and two of the wounded were from Mauritania. The third injured peacekeeper was from Zambia.

Dujarric said the Mauritanian was the 14th peacekeeper killed in Central African Republic this year.

U.N. Secretary-General Antonio Guterres condemned the death and injuries, and urged Central African authorities to swiftly investigate the incident and bring the perpetrators to justice, Dujarric said later. Guterres said attacks on U.N. peacekeepers may constitute war crimes.

The secretary-general reiterated the determination of the U.N. peacekeeping mission “to protect civilians and contribute to the stabilization of the Central African Republic,” the spokesman said.

The country has been wracked by violence between Muslims and Christians since 2013, when predominantly Muslim Seleka rebels overthrew the Christian president and seized power.

Dujarric said Guterres urges all parties to cease violence and work together to bring peace and stability to the country.