French authorities have arrested three people on suspicion of spying for Russia and acting to promote its war propaganda, as part of a probe into a French-Russian association, prosecutors said Tuesday.

Axar.az informs, citing France 24, one of those detained, a 40-year-old Russian man, was seen on video surveillance footage in September putting up pro-Russian posters on the Arc de Triomphe in Paris, the city's prosecutors' office said.

The man then reported by telephone to the head of the association, SOS Donbass, a woman also aged 40, who was suspected by French counter-espionage officials of trying to get economic information from French company executives.

The woman, who was born in Russia, had been on the radar of France's domestic intelligence service, the General Directorate for Internal Security (DGSI), since at least the beginning of the year.

After the DGSI detected "actions likely to harm the fundamental interests of the nation" relating to her, an investigating magistrate was appointed in March to probe various suspected offences including "collusion with a foreign power", which is punishable by 10 years in jail.

SOS Donbass presents itself as a humanitarian organisation offering aid to civilians in the eastern Donbas region of Ukraine, which is partially under Moscow's control.

The third person in custody is a 63-year-old man born in the northern Paris suburb of Seine-Saint-Denis.

A fourth suspect, 58, was spared pre-trial detention but placed under strict supervision and forced to report to the police station once a week.