Two Niger journalists have been jailed for 18 months over an article which criticised PM Hama Amadou.
The prime minister was alleged to prefer Iran to Western powers
The publisher and editor of Le Republicain, Maman Abou and Omar Keita Lalo, were also fined $10,000 (£5,250) for spreading false news.
The article said Mr Amadou preferred ties with Iran to those with the West.
It also questioned whether Mr Amadou was paying enough attention to human rights and to ensuring transparency in the handling of public funds.
The BBC's Idy Baraou in the capital, Niamey, says the atmosphere outside the courtroom as the sentence was announced was tense.
Heavily armed anti-riot units were deployed to stop hundreds of family members and sympathisers from entering the court, he says.
The case of the two journalists has been taken up by international media freedom organisations, which accuse the Niger judicial authorities of being unfair.
Their defence lawyer says an appeal against the verdict has been launched and the ruling will take place on 11 September.