A Tunisian jailed since 2012 for posting caricatures of Prophet Muhammad online has received a presidential pardon, an official said on Wednesday, but it was unclear whether he would be released.

President Moncef Marzouki on Wednesday announced on his official Facebook page that Jabeur Mejri had been granted a "special pardon" without providing further details.

President signed the pardon for Mejri concerning the "main case", the president's spokesman Adnene Manser told Shems FM radio on Wednesday.

However, the spokesman said "we were surprised by the existence of another (criminal) case", without elaborating.

The Tunisian head of the International Federation for Human Rights, Mokhtar Trifi, who has been closely following the case, said he was unaware of any other allegations against Mejri.

"We have absolutely no knowledge of any other case," he told AFP news agency.

'Public decency'

Mejri, who comes from Mahdia, south of the capital Tunis, is serving a seven-and-a-half year sentence for posting cartoons of the Prophet on his Facebook page.

Since the penal code does not punish blasphemy, he was convicted of transgressing morality, defamation and disturbing public order.

Tunisia's prisons authority did not immediately respond to a request for comment.

Mejri and his co-defendant Ghazi Beji, both unemployed and atheists, were charged with "publishing works likely to disturb public order" and "offence to public decency".

Beji fled abroad and was given asylum in France last June.

Marzouki had said on several occasions he wanted to free Mejri, but warned it would be difficult so long as Tunisia faced a rising threat from armed groups.