The Permanent Strategic Framework (CSP), an alliance of rebel forces, said it had decided to set up roadblocks across all roads leading to the country's borders with Mauritania, Algeria and Niger.

The blockade would control access to the cities of Menaka, Kidal, Gao, Timbuktu and Taoudeni and cover all products and means of transport, said the CSP statement.

The mainly Tuareg rebel forces have in recent weeks lost ground to a Malian army offensive that in mid-November saw them recapture the northeast city of Kidal.

Fighting between the separatists and government troops broke out again in August after eight years of calm, as both sides scrambled to fill the vacuum left by the withdrawal of UN peacekeepers.

The force, known as MINUSMA, packed up and left at the behest of Mali's military rulers in Bamako, where the colonels seized power in 2020.

It was the army's air power, including planes and drones, that helped make its recent gains against the rebel forces.

Mali's army was also backed by mercenaries from Russia's Wagner force, according to the rebels and local elected officials, but the regime denies the presence of the controversial private security group.

There have also been accusations of atrocities committed against civilians during the recent offensive by Mali's army and the Russian force, which the authorities have repeatedly denied.

The Malian army said in a statement late Wednesday that it had learned "of the kidnapping of some (its) soldiers" during an attack last week in the central town of Farabougou.

It denounced it as "a cowardly act" committed to "demoralise" soldiers and said that "everything will be done to allow the hostages to regain their freedom". It gave no number of captured soldiers.

In two separate videos seen by AFP, two people in military uniforms speaking in French and the local Bambara language claimed to be Malian soldiers taken hostage by the Al-Qaeda-linked coalition Support Group for Islam and Muslims (GSIM) following the Farabougou attack.

They called on the Malian authorities to secure their release.

Local sources told AFP last week that the attack on Farabougou killed dozens of soldiers and civilians.

Getting reliable information from the vast, northern part of Mali is extremely difficult because of its inaccessibility, lack of security and the muzzling of dissident voices there.