UN peacekeeping mission MINUSCA said it had conducted airstrikes in the Central African Republic Sunday against a "heavily armed" group of fighters advancing on the city of Bambari.

This is the second time in as many weeks the UN has fired on gunmen moving toward the central city.

In a statement, MINUSCA said it spotted about 40 fighters from the Popular Front for the Renaissance of the Central African Republic (FPRC), "heavily armed with AK47s and RPGs (rocket propelled grenades)" on Sunday morning a few kilometres north of Bambari.

It remained unclear whether the airstrikes resulted in any casualties, though the mission alerted the International Red Cross for any possible injuries, a MINUSCA spokesman told AFP.

The region has seen rising violence as the result of a conflict between the FPRC and a rival group, the Union for Peace in Central Africa (UPC).

The two factions have been fighting for control of taxes levied on Fulani herders during the current seasonal migration.

On Tuesday, MINUSCA said four of its officers were injured by FPRC fighters in the village of Ippy, about 100 kilometres (62 miles) northwest of Bambari.

On the weekend of February 11, UN attack helicopters opened fire on about 300 men advancing on Bambari in pickup trucks mounted with machine guns.

Following the offensive, the UN Security Council "urged the armed groups to immediately halt the fighting and join the peace and reconciliation dialogue".

The United Nations has deployed 12,000 peacekeepers to the Central African Republic to help restore stability following a war in 2013 that erupted after the overthrow of leader Francois Bozize, a Christian, by Muslim rebels from the Seleka coalition.