Controversial French comedian Dieudonne M'bala M'bala has been detained by police for a Facebook comment appearing to back Paris gunman Amedy Coulibaly.
His is one of dozens of cases opened by authorities in a crackdown on condoning or threatening terrorism.
Justice Minister Christiane Taubira said words of hatred and contempt had to be fought with the "utmost vigour".
Dieudonne already has convictions for inciting anti-Semitism and the courts ****** several one-man shows last year.
A judicial source quoted by AFP news agency said he was due to be released on Wednesday evening but would face trial at a later date.
The justice ministry said earlier that 54 cases had been opened since the ******* of 17 people in Paris last week. Of those, 37 cases involved condoning terrorism and 12 were for threatening to carry out terrorist acts.
The justice minister said prosecutors should act firmly and quickly against anyone found condoning terrorism or carrying out racist or anti-Semitic acts.
Dieudonne is already facing an inquiry into whether he condoned terrorism in a video in which he mocked the ************ of US journalist James Foley by Islamic State militants.
If found guilty, he could face up to seven years in jail and a €5,000 (£3,800; $5,900) fine.
Hours after 3.7 million people took part in rallies across France on Sunday, with the biggest in the centre of Paris, Dieudonne said on his Facebook page that the "historic" march had been as magical as the Big Bang that had created the universe.
"I'm finally going home," he wrote. "Know that this evening, as far as I'm concerned, I'm feeling like Charlie Coulibaly [French: je me sens Charlie Coulibaly]."
He combined the "Je suis Charlie" ("I am Charlie") slogan adopted across the world in support of the 17 victims of the Paris attacks with the name of one of the three Paris gunmen, before deleting the remark a short time later.
Coulibaly ****** a policewoman near a Jewish school last Thursday before going on to hold up a kosher supermarket the following day when he ******** four Jewish hostages.
