Ukraine abducted two soldiers from Crimea, says Russia
Russia has accused Ukraine of abducting two of its servicemen from the Crimean peninsula, which it annexed in 2014.
The Russian defence ministry said the men were "illegally detained" on Sunday.
Ukraine says the pair are deserters, who defected to Russia from the Ukrainian military after Crimea was annexed by Russian forces in 2014.
Russia called their arrest "another act of gross provocation" and called for their "immediate return".
The men have been named as Ensign Maxim Evgenyevich Odintsov and Junior Sergeant Alexander Vyacheslavovich Baranov.
Russia said they were taken from Crimea to Ukraine's Mykolaiv region, north-west of the peninsula.
The Security Service of Ukraine (SBU) said the detainees were apprehended after crossing into Ukrainian-controlled territory.
"We did not abduct anyone - we arrested two deserters who had crossed the border at the Chongar checkpoint," said SBU spokeswoman Elena Gitlyanskaya, quoted by Ukraine's Unian news agency.
She said the pair were now under criminal investigation.
'Confessions and sabotage'
In a statement, the Russian defence ministry accused Ukraine's security agencies of "fabricating" criminal charges against the two soldiers "for crimes allegedly committed against Ukraine".
It warned that "psychological and physical pressure" could be exerted on them to produce confessions.
Relations between Russia and Ukraine are at freezing point after Russia's annexation of the Crimean Peninsula more than two years ago, and support for pro-Russian insurgents in eastern Ukraine.
According to a Black Sea Fleet official, quoted by Russia's RT news, the two Russian soldiers were "lured" across the border by the SBU via intermediaries. The soldiers had been told that they could collect Ukrainian higher education certificates, it reported.
Earlier this month, a number of Ukrainian citizens were arrested in Crimea and accused of plotting acts of sabotage against Russia.
Several men were shown on Russian TV confessing to the claims.
Ukrainian officials have rejected the accusations.
Ukraine's chief military prosecutor, Anatoliy Matios, said in February that only 6,010 Ukrainian military staff had returned to mainland Ukraine from Crimea since Russia's annexation of the peninsula. There were 20,315 based in Crimea at the time of the annexation.
Those who remained in Russian-controlled Crimea were automatically accused of desertion, he said.
Those still in Crimea, he said, included 9,500 Ukrainian army soldiers, 1,386 national guards, 1,350 border guards and 1,372 SBU staff.
Mr Matios said the Ukrainian prosecutors were receiving almost daily amnesty requests from Ukrainian service personnel still in Crimea, who wanted to return home, Gazeta.ru news reported.