MOSCOW (AP) - Russia accused Ukrainian officials on Wednesday of barring crews of Russian commercial airlines from going outside their planes in Ukrainian airports.

MOSCOW (AP) Russia accused Ukrainian officials on Wednesday of barring crews of Russian commercial airlines from going outside their planes in Ukrainian airports.

Tensions between Moscow and Kiev have been rising since Russian forces occupied the Crimean Peninsula and stayed there throughout the referendum earlier this month where votes overwhelmingly supported Russia's annexation.

Russia's foreign ministry said in a statement that Ukrainian border guards have been forcing cabin crews of Aeroflot, the state-controlled Russian airline, to stay inside their planes. The ministry said the decision violates international law and ultimately "poses a threat to the safety of civil aviation" because the crews cannot rest properly.

The ministry said that it had sent protest notes twice to the Ukrainian embassy in Moscow.

Russian authorities previously complained that Ukrainian border guards have singled out Russian men at the frontier and blocked their crossing, fearing that they may be activists coming to stir up unrest.

Ukrainian soldiers on Tuesday began their westward journey from Crimea after Ukraine's fledging government ordered the withdrawal of its troops from the Black Sea peninsula.