N'DJAMENA - At least 37 people have been killed in fresh fighting this week between rival ethnic groups in Chad, President Idriss Deby said on Friday.

The violence broke out over three days in the eastern province of Ouaddie, a strategic area on the border with Sudan, he said.

"The intercommunal conflict has become a national concern," Deby told a press conference to mark the country's independence day. "We are witnessing a terrible phenomenon."

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.

The latest fighting erupted on Monday in the village of Hamra after a rancher was killed, according to a local charity.

The violence continued on Tuesday in the Chakoya locality, a local tribal official told AFP.

One hospital source told AFP the death toll was as high as 44.

Describing the clashes, Deby said that police sent to the scene came under fire.

"Gun owners do not hesitate to shoot the police. It is a total war... we must engage against those who carry weapons and killing people," he said.

Deby said he would visit the area in the future, without giving any timeframe.

Last month Deby, who has been in power for almost three decades, hinted that military courts may be reintroduced in a bid to curb the unrest, a suggestion denounced by the country's opposition.