The on Monday sharply criticised the opening of a rail link between Russia and the annexed Crimean peninsula, calling it "another violation of Ukraine's sovereignty".

The statement was issued hours after Russian President Vladimir Putin rode in the driver's cabin of a train marking the inauguration of the route starting from the city of Kerch in Crimea, the Ukrainian peninsula that Russia annexed five years ago.

The rail link passes over a 19-kilometre (12-mile) long bridge that was built by a company owned by a billionaire businessman ally of Putin's.

Ukraine's government and Western countries view Russia's annexation of as illegal. Ukrainian forces continue to battle Russia-backed fighters in the east in a lingering separatist conflict that has claimed 13,000 lives since 2014.

The statement from the EU underlined that the railway on the Kerch bridge was built "without Ukraine's consent" and was "yet another step towards a forced integration of the illegally annexed peninsula".

Additionally, it added, "the bridge limits the passage of vessels through the Kerch Strait to Ukrainian ports in the Azov Sea" which it said must remain unhindered under law.

"The does not and will not recognise the illegal annexation of the Crimean peninsula by Russia," it said.

The this month extended by another six months economic sanctions on Russia imposed over the conflict in Ukraine.