The claim is part of an emerging pro-Kremlin smear campaign targeting Belarusian journalist and activist Raman Pratasevich.
There is no substantial evidence to suggest that Mr. Protasevich ever participated in the military activity of the Azov battalion. Protasevich himself said in an interview with a Russian journalist in 2020 that he had been in the war zone in Eastern Ukraine as a freelance journalist. This was further confirmed by Andriy Biletskyy, former commander of Azov. He said Pratasevich had been present in the Donbas warzone, but his activity there was limited to covering the course of the conflict as a journalist. See further investigation by an independent outlet Meduza.
Pratasevich was detained in Minsk airport when flying from Athens to Vilnius. On Sunday, May 23, 2021, the Ryanair flight from Greece to Lithuania was forced to turn back before crossing the Lithuanian border and land in the Belarusian capital. The pretext for landing in Minsk was a false report about the bomb on board. At the moment when the plane changed course, it was closer to Vilnius airport than to Minsk. The plane was forced by a Belarusian military aircraft to land in Minsk. Pratasevich was detained during a repeated security check of passengers.
The EU condemned Belarusian action against a civil plane and the detention of Pratasevich. In a declaration on behalf of the EU on the forced diversion of Ryanair flight FR4978 to Minsk on 23 May 2021, the High Representative called for the immediate release of Mr Protasevich. This was followed by a European Council statement, in which the EU leaders called for targeted individual and economic sanctions as well as to ban overflight of EU airspace by Belarusian airlines and prevent access to EU airports of flights operated by these.
For further reading, see here for an overview of the ongoing pro-Kremlin campaign to label Pratasevich as a neo-Nazi.