Zvinchuk, a former press officer at Russia's defence ministry with reported ties to Russian intelligence services, was detained on Friday alongside his wife and three other Russians by police and security agents in the Adriatic resort town of Risan, local media reported.
The group was taken to Podgorica, Montenegro's capital, for questioning and their phones and passports were confiscated, according to the Russian Telegram news channel Baza, which said Zvinchuk was detained at the luxury Mövenpick hotel in Risan.
Prime Minister Spajić confirmed the detention in a post on X, saying it followed warnings that the country would face attempts at destabilisation and hybrid warfare.
Rybar, founded in 2018 by Zvinchuk, is one of the most popular Russian military blogs covering the war in Ukraine, with more than 1.5 million subscribers on Telegram. It forms part of a sprawling online media ecosystem that promotes Vladimir Putin's invasion of Ukraine.
The channel's activities extend beyond Ukraine, with Rybar promoting pro-Kremlin narratives in Africa and the Middle East. It has more recently been accused of amplifying far-right narratives surrounding the migration crisis in Ceuta, a Spanish enclave in north Africa.
In a post on Telegram, the Rybar channel said its team was in contact with Russia's foreign ministry, which was working to resolve the situation. "Since there were no violations of local legislation, we expect all detainees to be released," the channel said.