TUNIS (AFP) - Tunisian authorities have arrested a blogger as he returned from a trip abroad weeks after he was convicted of defaming army officers, his lawyer said Thursday.

Yassine Ayari, 33, was taken into custody overnight after landing at Tunis-Carthage airport and was whisked to jail in line with the court verdict pronounced against him.

The military prosecutor said Ayari had been sentenced in absentia on Nov 18 to three years' jail on charges of having "defamed army officers and senior defence ministry officials".

Ayari, who was returning from France when he was detained overnight, had accused these officials of financial abuse, the prosecutor said in a statement.

The blogger was unaware of the verdict against him for "undermining" the army, his lawyer Sami Ben Amor said, adding that the verdict was "very harsh".

Ayari, who has posted on Facebook that he stands by every word he has written, has appealed the charges against him and a new hearing in the case has been set for Jan 6, Ben Amor said.

"This case undermines freedom of speech and is the first of its kind to emerge under the reign of Beji Caid Essebsi," said the lawyer, adding that "Yassine Ayari is paying the price of his political views".

Essebsi, an 88-year old anti-Islamist, won Tunisia's first free presidential election on Sunday, capping off the transition to democracy in the birthplace of the Arab Spring.

His victory follows October legislative polls won by his Nidaa Tounes party.

In recent months, Ayari had published blogs very critical of Nidaa Tounes.

Essebsi is a veteran politician who served under previous Tunisian regimes, including in the government of autocratic president Zine El Abidine Ben Ali who was ousted in the 2011 uprising.