Leyla Abdoullayeva told Reuters the French citizen, Martin Ryan, was arrested on Dec. 4 on "suspicion of carrying out acts of espionage".

France's foreign ministry did not immediately comment.

Ties between Paris and Baku have been strained in recent months and have worsened since Baku took control of the Nagorno-Karabakh region.

Abdoullayeva said legal authorities in Azerbaijan had ordered Ryan be initially held for four months and that the French embassy had been notified of the arrest.

Baku on Dec. 26 expelled two French diplomats saying they were acting in a way that was "incompatible with their diplomatic status".

France's foreign ministry, which denied the Azeri claims, the next day summoned Abdoullayeva and said it was expelling two Azeri diplomats in response.

At the time of the Nagorno campaign, France repeatedly criticized Azeri authorities over the blocking of the Lachin corridor, the key road that linked Armenia to the disputed Nagorno-Karabakh enclave. It has since provided military equipment to Armenia.

In November, France's cyber defence unit uncovered a disinformation campaign emanating from Azerbaijan that aimed to undermine Paris's capacity to hold next year's Olympic Games, according to a report seen by Reuters.

(Reporting by John Irish; Editing by Nick Macfie)