Four dead in army, police clashes in Nigeria: source

The police confirmed the fracas in the state capital of Damaturu, but did not say if there were casualties.

"The Nigeria police force is abreast of the unfortunate incident that occurred in the early hours of today 12th April, 2017 in Damaturu between the personnel of the force and that of the Nigerian army," police spokesman Jimoh Moshood said in a statement.

He said an investigation had been launched to determine "the causes of the incident and deal with the situation appropriately to prevent such occurrence in the future".

The army authorities were not immediately available for comment.

A security officer who did not want to be named, told AFP trouble began on Tuesday when an army officer in a mufti (civilian dress) ran into a convoy of the head of the police mobile unit in Damaturu.

"The army officer was beaten up by the police for his action. This morning, soldiers stormed the police station and took away the head of the mobile unit to their military base," he said.

He said the the soldiers' action angered some police officers who invaded the army base to free their boss.

"There was a shootout in which a soldier and a policeman were killed on the spot while two policemen who were injured later died of their wounds," he said.

Yobe and two other states -- Borno and Adamawa -- in the northeast are the worst-hit in the eight-year Boko Haram Islamist insurgency in Nigeria.

Boko Haram, which aims to impose a hardline Islamist legal system in Nigeria's mainly-Muslim north, has killed some 20,000 people and forced 2.6 million others to flee their homes since 2009.

A joint military operation, comprising Nigerian army, navy, airforce and the police, and aided by regional forces, is currently battling the jihadists.