Abba has been detained in "extremely difficult" conditions for more than one year and four months and recently had to spend time in hospital, the management of RFI and its parent company France Médias Monde said in a statement on Tuesday.
After numerous hearings a government commissioner acknowledged that witnesses, who were supposed to have proof of his guilt on charges of complicity with terrorist acts and failure to inform on such acts, did not in fact exist, the statement said.
"We are defending this journalist who was doing his job and is detained in conditions that we cannot accept," Ayrault said on RFI on Tuesday morning.
If found guilty, Abba, who was arrested because of his coverage of the Boko Haram movement based in neighbouring Nigeria, could face the death penalty due to a controversial anti-terror law passed in 2014.
France Médias Monde reaffirms that Ahmed Abba is innocent and expresses the hope that tomorrow he will finally be acquitted.
The CGT union on Monday denounced his trials as a "judicial mascarade".