The US-based Committee to Protect Journalists said at least eight Ethiopian journalists have been detained since August 2023.
French journalist Antoine Galindo was released by Ethiopian police on Thursday after a week, his employer said.
He was arrested last Thursday while on assignment in the country's capital Addis Ababa on charges of "conspiracy to create chaos".
Galindo has left for France and is due to arrive on Friday, the publisher of Africa Intelligence, Quentin Botbol, said in an emailed statement.
Human rights activists have repeatedly criticized 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 said 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 before Galindo were two Swedish journalists in 2011.