The General Directorate of Military Intelligence (DGRM) said in a statement that "a well-organised group of individuals within the M3M movement tried to undermine the security of the state".

The statement, sent to AFP by Communications Minister Abderaman Koulamallah, said the group members were arrested on January 12, a day before "they had the intention of carrying out insurrectional operations".

The DGRM statement gave no further details about the "operations".

But it went on to state that: "Unable to carry out their aims with guns... (they) resorted to occult beliefs with three witch doctors...(who) asked them to make sacrifices by burning chicks, goats, sheep and in the end a man".

The DGRM said a decapitated head had been found "in a bag at the home of the president of M3M," a previously unknown group.

The president was said to be a "lieutenant".

The army supplied certain Chadian media with video footage showing a DGRM general before dozens of men sat on the ground after being "arrested".

Chad has been led by general Mahamat Idriss Deby Itno since the army named him as transitional president in April 2021 following the death of his father who ran the desert nation with an iron fist for 30 years.

The 37-year-old son heads a junta of 15 generals and had first promised to restore civilian rule through elections within 18 months.

The junta has since prolonged that period by two years.

Presidential and legislative elections are now expected to take place before the end of October.

Mahamat Deby has been designated by his father's Patriotic Salvation Movement (MPS) to stand for president.