A local official and a soldier in the column, speaking on condition of anonymity, said the convoy of several dozen vehicles had reached Tarkint, about 200 kilometres (120 miles) south of Kidal.

The troop movements, which began on Monday, have triggered speculation about the launch of an offensive in the Kidal region which has recently seen increased activity by predominantly Tuareg armed groups and from jihadist attacks.

The Al-Qaeda-affiliated jihadist alliance Support Group for Islam and Muslims (GSIM) claimed responsibility on social networks for a bomb attack on the convoy, which it said also included mercenaries from the Russian security group Wagner.

No Malian official has officially said the troops are headed for the town of Kidal.

One senior military official indicated that the convoy was due to travel further north to Aguelhok and Tessalit, from where UN peacekeepers will soon pull out.

But army information services chief Colonel Souleymane Dembele has declared that in the long term, Kidal -- which has for years been governed by the Coordination of Azawad Movements (CMA), an alliance of predominantly Tuareg armed groups who have recently resumed combat against the army -- had to come back under state control.

The UN MINUSMA force has been handing over its camps to Malian authorities, but the separatists claim they should be returned to their control.

The UN mission has still to vacate its camp at Kidal and two other sites further north by the end of December.

Kidal lies more than 1,500 kilometres from the capital Bamako.

When an insurrection broke out in 2012, the region was one of the first in Mali to fall into the hands of the rebels, both separatists and Salafists.

It was taken over by the CMA in 2013 following military intervention by France, and has remained in their hands despite a 2014 attempt by the Malian army to regain control.

In 2015, the rebels signed the so-called Algiers peace agreement with pro-government armed groups and the state.

The agreement is now considered defunct following August's resumption of hostilities.