Russian Foreign Minister Sergei Lavrov on Tuesday accused Ukraine of "illegally" detaining two Russian soldiers by the Crimean border, calling the incident "a provocation."

Kyiv maintains that the two men were deserters from the Ukrainian army and were detained in a Ukrainian-controlled territory after crossing the border.

However, Moscow claims that they were seized in Crimea, which was controversially annexed by Russia in 2014.

Russia's Foreign Ministry late on Monday released a statement saying that it considered that "these actions of the Ukrainian special forces toward Russian citizens are yet another gross provocation." It demanded the two men's swift return to Russia.

The two soldiers were reportedly detained by Ukrainian security services on Sunday at around 1 p.m. Moscow time (1000 UTC). They have been named by Russia as Maxim Odintsov and Alexander Baranov.

Increasingly strained ties

Moscow and Kyiv have been at odds over Russia's annexation of the Black Sea Peninsula in 2014 by sending thousands of special forces to take control of Ukrainian bases. Crimea then held a hastily organized referendum in which it voted to become part of Russia. The vote was subsequently rejected by the international community.

Since the annexation, Russia has accused Ukrainian intelligence of orchestrating attempted terror attacks on Crimea. In August, Russian President Vladimir Putin openly accused Kyiv of attempting to conduct military incursions into the disputed region. Kyiv vehemently denies the accusations.

The allegations have ratcheted up tensions between the two ex-Soviet neighbors, additionally strained by a long and bloody insurgency by pro-Russian rebels in eastern Ukraine that Kyiv and several Western countries say is being actively supported by Moscow.

dm/tj (AFP, Reuters)