Russia says two of its servicemen have been abducted by Ukraine’s security officials in Crimea, demanding their immediate release.

The Russian Defense Ministry said in statement that the pair was “illegally detained” on Sunday and whisked across the border to the territory of the Nikolayev region in Ukraine.

The ministry identified them as warrant officer Maxim Yevgenyevich Odintsov and junior sergeant Alexander Vyacheslavovich Baranov.

Kiev, it said, conducted the abduction with the apparent aim of exerting “psychological and physical pressure” to have them make confessions needed by the Ukrainian side.

“We consider these actions taken by Ukrainian security services against Russian citizens as another flagrant provocation and demand their immediate release to Russian territory,” the ministry said.

"We think it was a provocation," Russian Foreign Minister Sergei Lavrov was quoted as saying on Tuesday.

Russia's official TASS news agency, citing unnamed sources, also said that Kiev was trying to "fabricate a criminal case" against the abductees on charges of alleged crimes against Ukraine.

Kiev said the pair had been arrested in a Ukrainian-controlled territory after allegedly crossing the border at Chonhar, a village at the northeastern coast of Crimean Peninsula. It said the servicemen had served in the Ukrainian army before deserting to Russia.

The new development can further escalate already tense tensions between the two countries. Relations between Moscow and Kiev strained after the Crimean Peninsula rejoined Russia in a referendum in March 2014.

The ties deteriorated further after Kiev started a military crackdown in the two mainly Russian-speaking regions of Lugansk and Donetsk in the east, where there is a push for greater autonomy from Ukraine.

According to the United Nations, some 10,000 people have lost their lives and over 21,000 others have been injured in the conflict since April 2014.

Russian bank under attack in Ukraine

On Monday, a group of angry demonstrators smashed windows and ransacked the Sberbank of Russia branch on Leo Tolstoy Square in the Ukrainian capital Kiev.

The attackers were part of a much larger demonstration, comprising of thousands of people, which convened in the capital to commemorate the third anniversary of the deadly pro-West protests.

The protests, first staged on November 21, 2013, led to the ouster of president Viktor Yanukovych who was a key ally of Russia.

Armed groups then took to the streets and fought pitched battles with government forces after Yanukovych decided not to sign an association agreement with the European Union.

Some sporadic scuffles broke out between groups of rival protesters and security forces on Monday evening but no casualties were reported.