At least 13 people have been killed during clashes between rival armed groups in the Central African Republic.

A UN official said the fighting began on Wednesday morning after a faction of the Popular Front for the Rebirth of Central Africa (FPRC) attacked the town of Ndélé, in the northern province of Bamingui-Bangoran.

A civil war that began in 2013 has displaced more than four million people in the country.

A year ago a peace deal was signed between the government and 14 armed groups, but there have been frequent outbreaks of violence since then as rival groups compete for control of mineral resources.