Antoine Galindo was arrested last Thursday while on assignment in the capital Addis Ababa, the Africa Intelligence publication said in a statement. It said a judge on Saturday prolonged Galindo's detention until 1 March.
Spokespeople for Ethiopia's government and police did not immediately respond to requests for comment. The French embassy in Addis Ababa also did not respond to a request for comment.
Africa Intelligence said Galindo "has been suspected of 'conspiracy to create chaos in Ethiopia' and was brought before a judge on 24 February." The publication said its lawyer attended the hearing and was told about the charges.
"Africa Intelligence condemns the unjustified arrest ... and calls for his immediate release," it said.
Human rights activists have repeatedly criticised Ethiopia's restrictions on press freedom, particularly in response to critical coverage of conflicts and security crises.
The New York-based Committee to Protect Journalists says at least eight Ethiopian journalists have been detained since August.
Foreign journalists have been expelled from Ethiopia or denied accreditations to work in recent years, but the last to be arrested were two Swedish journalists in 2011.
They were sentenced to 11 years in prison for helping and promoting a rebel group and entering the country illegally before being pardoned and released the following year.
Prime Minister Abiy Ahmed freed dozens of jailed members of the media when he came to power in 2018 as part of a raft of political reforms.
But critics say his government has cracked down hard on dissent as civil conflicts, including a 2020-2022 war in the northern Tigray region, have broken out.
Abiy says he is guaranteeing stability and law and order in the multi-ethnic nation.
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