A Rwandan soldier serving with the United Nations peacekeeping mission in Central African Republic has shot dead four Rwandan troops and wounded eight others before killing himself.

The incident happened at 5.45am on Saturday at the Rwandan battalion headquarters in Bangui, the CAR capital, according to a Rwandan defence ministry statement.

The Rwandan Defence Force is investigating the killings with terrorism and the mental wellbeing of the suspect killer among its lines of inquiry.

“Investigations have immediately commenced to establish the motive behind this deplorable shooting of his RDF colleagues,” Brig Gen Joseph Nzabamwita said. “We suspect terrorism without ruling out mental illness to be the cause.”

Fighting has gripped CAR since early 2013, when mostly Muslim Séléka rebels seized power in Bangui, sparking reprisal attacks from Christian militias.

A report released by the International Rescue Committee (IRC), based on research in March, said 6,000 people have been killed since the conflict began and 2.7 million – more than half the country’s population – are in need of emergency assistance.

The Rwandan forces are supporting Minusca, the UN peacekeeping operation in CAR, which has been deployed since April 2014.

Rwanda is among the top 10 countries in the world for providing peacekeeping troops and has more than 850 soldiers deployed in the CAR.

Claire Bourgeois, the UN humanitarian coordinator for CAR, said in April the country’s troubles were in danger of “becoming a forgotten crisis” and that more funds needed to be raised to protect displaced people and provide humanitarian support.