A court in Crimea has ordered one of the 24 Ukrainian sailors captured by Russia at the weekend to be detained for two months, Russian media has reported.
The man faces a charge of illegally crossing Russian borders, which carries a sentence of up to six years in prison, Russian news agencies quoted an investigator as saying.
Russian border forces fired on and seized three Ukrainian ships in the Kerch strait, which separates Crimea from the Russian mainland, on Sunday. At least three sailors were wounded. Ukraine says they were travelling in shared waters on a routine passage to the Sea of Azov, which they have a right to patrol under a bilateral treaty.
The sailors are being be arraigned at a court in the city of Simferopol in Crimea, the peninsula annexed by Russia in 2014.
The decision to launch prosecutions is likely to deepen the latest crisis between the two countries, which has provoked international condemnation and talk of fresh western sanctions against Moscow.