Deadly clashes are unfolding in a troubled gold-mining region in northern Chad, pitching government troops against a local "self-defence" force, sources said.
Fighting broke out on Saturday in Miski, in the heart of the Tibesti mountains near the Libyan border, and resumed this week with the loss of several lives, the sources on both sides said.
Two of the dead are senior officers of the elite presidential guard, Isakha Djeroua and Abdelkerim Mustapha, a military source said.
Chadian forces shelled the area on Monday and Tuesday and deployed two helicopters, one of which has crashed, and two Sukhoi warplanes, added a military source.
The Tibesti region has been hit by a gold rush, with an influx of illegal miners - locals or people from other Chadian regions or other countries - that has stoked unrest with locals.
In August, the armed forces carried out several offensives aimed at "clearing out" the illegal miners, and at fighting cross-border incursions from Chadian rebels who have holed up in Libya.
The crackdown led to the creation in early November of an armed "self-defence committee".
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Its spokesperson, Mouli Sougui, a former deputy prefect for Yebbi-Bou district, told AFP on Tuesday that the group did not rule out an alliance with Chadian rebels in Libya, who have made advances into the north of the country since August.
President Idriss Deby's son, General Mahamat Kaka, is in charge of operations in the north.
Last week, Deby carried out a major reshuffle of his security apparatus.
General Daoud Yaya, who formerly headed the gendarmerie, was appointed defence minister, replacing Bichara Issa who was dropped from the cabinet.
Mahamat Abba Ali Salah, a northerner and the governor of the troubled Lake Chad region which has been ravaged by attacks staged by Boko Haram jihadists from Nigeria, was appointed the new interior and security minister.
Deby is one of Africa's longest-serving leaders.
He took over the arid, impoverished nation in 1990 and won a disputed fifth term in April 2016.