"The EU considers the case to be in breach of international law and elementary standards of justice. The EU continues to call on the Russian Federation to immediately release Sentsov and Kolchenko and to guarantee their safe return to Ukraine," she said in her statement on the sentencing by a Russian court of Ukrainian citizens.

According to Mogherini, Russian courts are not competent to judge acts committed outside the internationally-recognised territory of Russia.

"The EU has consistently followed the case of Sentsov and Kolchenko. Known to oppose the illegal annexation of the Crimean Peninsula by Russia, they were arrested in May 2014 in relation to alleged activities conducted on the peninsula."

As UNIAN reported earlier, the military court in Russia’s city of Rostov-on-Don on Tuesday sentenced Ukrainian film director Oleh Sentsov to 20 years in prison and Ukrainian activist Oleksandr Kolchenko to 10 years in prison, both were accused of terrorism and would be kept in a high-security penal colony.