Six UN peacekeepers were injured during an attack by unknown assailants who opened fire on a patrol northeast of the capital Bangui, amid a flareup of violence after months of relative calm.

The new UN peacekeeping MINUSCA force, in a statement late Saturday, condemned Friday's attack, which came a day after another UN peacekeeper was killed near Bangui.

The latest attack was carried out by "armed elements who opened fire on a MINUSCA police patrol... leaving four blue helmets injured".

Such attacks "must cease immediately" the statement continued, calling for a "durable peace".

"It is unacceptable that the blue helmets, who come from various places, should become the target of attack," it added, without giving the nationalities of those injured.

A UN peacekeeper from Pakistan was killed, and nine others injured, near the capital on Thursday.

It was the first peacekeeper death of the mission that deployed last month in the Central African Republic, taking over from African-led troops that were sent after a March 2013 coup plunged the country into bloodshed and chaos.

Bangui has been rocked by days of violence pitting the city's Muslim and Christian populations, leaving at least seven people dead and many dozens wounded, according to UN sources in Bangui.

The fresh spate of violence was apparently ignited by a grenade attack in a Bangui street blamed on a Muslim assailant on a motorbike, followed by the murder of a taxi driver allegedly by Muslim gunmen who set fire to several houses.

The UN's 130,000 troops, police and civilian staff serving in missions worldwide are being drawn into more complex conflicts while being tasked with enforcing fragile peace deals.