Archaeologist Alexander Butyagin is accused of conducting illegal excavations in Crimea - Ukraine's peninsula annexed by Russia.
Atesh, meaning fire in Crimean Tatar, says it collects data on Russian forces in occupied Ukraine.
Russian media is reporting fresh explosions and a fire in Crimea.
Father Ioann has been held under new laws for criticising the war.
He says an alleged plan to overthrow his government comes amid threats of a Russian invasion.
Nato's chief urges Russia to be transparent over its "large and unusual" massing of border forces.
The Russian president says last week's naval incident off Crimea was co-ordinated to test Moscow.
