Makichyan, 24, was reportedly detained in Moscow hours after returning from a trip to Madrid, Spain, where he spoke at the COP 25 UN Climate Change Conference together with climate activist Greta Thunberg, who he later joined for a youth-led protest in the city. Makichyan was one of the first activists in Russia to join Thunberg’s Fridays for Future movement, with weekly solitary pickets in central Moscow starting in March.

A Moscow court on Friday slapped climate change activist Arshak Makichyan with a six-day sentence for participating in an unsanctioned picket in Moscow.

A court handed Makichyan six days of administrative arrest for an unsanctioned picket he had participated in on Oct. 25, BBC Russia reported Friday.

The activist had been detained on that day and later released after unfurling a banner in central Moscow against climate change. BBC Russia cited his lawyer as saying that the authorities had denied him a permit for the protest.

Makichyan is one of Russia’s most prominent youth activists against climate change.

He spoke to The Moscow Times in April about his weekly pickets in central Moscow as part of the Fridays for Future movement.

"I know that not many people are willing to protest in Russia because most of the population doesn't understand what global warming is… so I decided to start it myself,” he said at the time.

Russia remain a relatively climate-skeptic nation, with recent polls saying that less than half of Russians believe climate change poses a major threat to their country.