Five police have been killed in violence in western Cameroon over the weekend, where English-speaking separatists have declared an independent state, reports AFP news agency quoting security sources and witnesses.

AFP says four security force officials were killed in Esu village in the North-West Region on Sunday morning when their unit came under attack.

The same day, a police officer was killed by unidentified attackers at his home in Mutengene, near the South-West region's capital of Buea.

The division between Cameroon's French-speaking majority and its English-speaking minority has its roots in the colonial era - when the former German colony was divided between Britain and France after World War I.

Cameroon later became a federation of two states - one English-speaking, the other French-speaking - under one president. Some people in the Anglophone regions want to return to this model, while others are calling for an independent, breakaway English-speaking state. Both ideas have been ruled out by President Paul Biya.

While there have been long-held grievances among some, this recent wave of protests by English-speaking Cameroonians - which began in 2016 against perceived discrimination and dominance by the Francophone majority - has increasingly turned violent.

Dozens of police and troops have been killed, as well as more than 100 civilians, according to a government report in July.

At least 21,000 people living in the Anglophone regions have fled across the border into Nigeria, and the UN estimates that a further 160,000 are displaced within Cameroon. Many others are still hiding in the forest.

Aid agencies' efforts to assist civilians have been frustrated by the struggle to access conflict areas.