The official, who requested anonymity, said soldiers had left the northern city of Gao and were on their way to Kidal. "There is no problem for now," he said.

Rebels captured much of the West African state's north in 2012, including Kidal, triggering a war that has since been taken over by jihadists and spread to central Mali, neighbouring Burkina Faso and Niger.

The return of Malian troops to Kidal is considered a key component in implementing the 2015 Algiers peace agreement, struck between the government in Bamako and some rebel groups.

Mali has struggled to contain the revolt, despite the presence of foreign troops.

Both the United Nations peacekeeping mission and French forces in the country support the Malian army's return to Kidal, the officer said.

Troops are expected to take several days to reach the city, which is about 200 kilometres (120 miles) south of Gao.

The units returning to the city are so-called "reconstituted" ones, comprised of regulars and former rebels who joined the military after the 2015 peace accord.

Other such units are expected to deploy in northern Malian cities such as Menaka, Gao and Timbuktu, after the soldiers reach Kidal.