The army in Chad said Friday it had wiped out "several hundred" rebels over two days of fighting in the country's west, where President Idriss Deby Itno suffered mortal wounds at the front line this month.

The army has since mid-April been fighting the Front for Change and Concord in Chad (FACT), drawn mainly from the Goran ethnic group, in the Kanem desert region along the border with Niger.

"On April 29, the defence and security forces finished dealing with the rebel band that intruded towards Nokou in northern Kanem," army spokesman Azem Bermandoa Agouna said in a statement.

Nokou is around 200 kilometres (125 miles) north of the capital N'Djamena.

Agouna tallied "several hundred rebels neutralised (and) 66 taken prisoner" while six soldiers were killed.

The military earlier said it had lost a helicopter during the fighting due to a "technical fault" but the rebels say they shot it down.

The rebels have threatened to march on N'Djamena, where a team from the African Union arrived Thursday to assess the situation and examine ways of a speedy return to democratic rule.

Immediately after Deby's death, a junta dubbed the Transitional Military Council (CMT) was quickly formed, chaired by Mahamat Idriss Deby, the late president's son, and made up of generals.

Assuming the title of president, the younger Deby dissolved the National Assembly and vowed to hold "free and democratic" elections in 18 months.

Deby, 68, died on April 19 from wounds he suffered fighting the Libya-based rebels, according to the authorities.

A career soldier who seized power in 1990 and exercised it ruthlessly for 30 years, Deby died on the day that the electoral commission confirmed that he had won a landslide victory, the authorities say.

FACT is led by Mahamat Mahadi Ali, a veteran insurgent who previously lived in France. It was formed in 2016 and has been based in southern Libya.

The group vowed to pursue its offensive after a pause for Deby's funeral on April 23. Experts believe FACT has between 1,500 and 2,000 fighters.

Chad police clash with opposition demonstrators in N'Djamena
Chad police clash with opposition demonstrators in N'Djamena AFP / Issouf SANOGO

Protests immediately erupted after the junta took power and claimed the lives of at least six people, according to officials.

Chadian police have denied opposition claims that they fired live bullets on demonstrators.

The younger Deby, under domestic and international pressure, has offered a "national dialogue" on the way forward.

Chad is a kelly ally of the West in the fight against jihadists in the restive Sahel region.

It has well-respected armed forces and hosts the headquarters of France's 5,100-strong Barkhane anti-jihadist mission.

It also partners Burkina Faso, Mali, Mauritania and Niger in a regional anti-jihad coalition called the G5 Sahel.

The unrest in Chad has once again put the spotlight on lawlessness in neighbouring Libya.

The UN Security Council on Thursday held its first meeting on the risk of mercenaries in warn-torn North African nation.

The closed-door session was requested by members Kenya, Niger and Tunisia, before Deby's death.

According to diplomats, there are estimated to be "more than 20,000" foreign mercenaries in Libya, whom Libyan authorities, UN officials and world powers have demanded leave.

However dispersal of the mercenaries -- who diplomats say include 13,000 Syrian and 11,000 Sudanese fighters -- could represent a new risk for the region.