Chad's presidency said in a statement that President Mahamat Idriss Déby has pardoned his main rival and opposition leader Success Masra, who has been in jail for more than a year for inciting violence and complicity to murder.

Masra, a former prime minister, was sentenced to 20 years and fined 1-billion CFA francs last year in a trial that was criticised by human rights activists as politically motivated.

Masra will be released in the coming days, the statement said, after the presidency agreed to a request for a pardon submitted by his attorneys.

Masra was internationally recognised as the most vocal figure in the opposition. He will be freed along with eight other political figures, the statement said.

"These nine individuals will be released as soon as the Ministry of Justice makes the necessary arrangements in the coming hours and days," the presidency said.

"They have been pardoned by the Head of State. However, the pardon does not waive the civil penalties, which remain enforceable."