The Northwest and Southwest regions of the west African nation have seen vicious fighting in the past four years, with the UN and international aid groups saying both army troops and anglophone rebels have committed abuses and crimes against civilians.

Overnight from Thursday to Friday, "separatists attacked the forward military post in Menfoung, leaving four soldiers dead and one seriously wounded," West regional governor Augustine Awa Fonka told state broadcaster CRTV.

The rebels often cross from Cameroon's Northwest into the West region to attack military outposts.

Members of the anglophone minority in the country's westernmost provinces had long complained of being marginalised by the French-speaking majority and 88-year-old President Paul Biya, in power for 38 years.

From 2017, their demonstrations devolved into a bloody conflict.

Under fierce international pressure, the government in Yaounde has acknowledged some crimes laid at the army's feet by aid groups and the UN, but mostly says they were the actions of "out-of-control" soldiers.

For their part, the rebels have extended their violent attacks against police and soldiers to civilians.

They increasingly kidnap people from schools that teach French, or murder those accused of "collaboration" with the government.

In the past four years, more than 3,500 people have been killed and over 700,000 have fled their homes to escape the conflict.