The attack comes after a state of emergency was declared just days ago.

"A soldier killed his boss before fleeing to take refuge in the police station," one of the sources said.

The family of the dead soldier tried to attack the police station in revenge, provoking a response from officers that left three dead and four seriously injured, the second source said.

On Sunday, President Idriss Deby Itno declared a state of emergency in two eastern regions, Sila and Ouaddai, after violent ethnic clashes killed more than 50 people earlier this month.

Eastern Chad is in the grip of a cycle of violence between nomadic camel herders -- many from the Zaghawa ethnic group from which Deby hails -- and sedentary farmers from the Ouaddian community.

A state of emergency was also declared in the north of the country in the Tibesti region, which borders Libya and where Bardai is the main town.