By Serife Cetin

BRUSSELS 

NATO on Thursday expressed concern over the “heightened tensions” between Russia and Ukraine for a naval confrontation in the Sea of Azov.

“We remain concerned by the heightened tensions in and around the Sea of Azov. There can be no justification for Russia's use of military force against Ukrainian ships and sailors,” NATO Secretary-General Jens Stoltenberg told a news conference after a meeting with Ukrainian President Petro Poroshenko at NATO headquarters in Brussels.

Stating that Ukraine is a “highly valued partner” of NATO, Stoltenberg called on Russia to release the seized sailors and ships immediately, and allow free navigation in the sea.

“This is part of Russia’s pattern of destabilizing behavior. We see that in eastern Ukraine, where cease-fire violations are reported daily,” he said, referring to latest developments in the Sea of Azov.

Russia seized two Ukrainian navy ships and a navy tugboat along with 24 crew members off Crimea in late November, accusing the vessels of entering its waters and provoking a conflict.

It said the vessels had ignored calls to stop, sparking military action.

Russia intervened as the Ukrainian ships were relocating from the Black Sea port of Odessa to the port of Mariupol in the Sea of Azov.

The action has further strained ties between Moscow and Kiev, which have been at loggerheads since 2014, when Russia annexed Crimea after a controversial referendum.

The international community views the annexation as illegal and the election Russia uses to justify it as illegitimate.

Stoltenberg went onto say that NATO provided Ukraine with strong “political and practical support”.

On his part, Poroshenko said Russia crossed “red line” by opening fire in international waters and they would not allow the incident to be “ignored”.

He also welcomed NATO’s support for his country against the Russian acts.

Russia's Investigative Committee has accused the Ukrainians of illegal border crossing.

In a tit-for-tat, Ukraine’s Poroshenko has forbidden Russian male citizens aged 16 to 60 from entering the country.