NATO Secretary General, Jens Stoltenberg, has reaffirmed the organisation’s support for Ukraine, amid tension between the eastern European nation and Russia.
Speaking at a meeting held for NATO foreign ministers, Mr Stoltenburg called on Russia to “immediately” release captured Ukrainian sailors and ships.
“In response to Russia’s aggressive actions, NATO has substantially increased its presence in the Black Sea region over the past few years at sea, in the air and on [the] ground,” Mr Stoltenburg told journalists.
“NATO ships routinely patrol and exercise in the Black Sea.
"This year ships under NATO command have spent 120 days in the Black Sea, compared to 80 days the year before.”
Russia claims disputed territorial rights over the Black Sea and has built a controversial bridge between Crimea and the Russian mainland.
Moscow has responded by announcing its own plans to increase combat capabilities and more military exercises, like Vostok-18, are expected.
Last month, the Secretary General said Russia was putting the INF Treaty "in jeopardy".
On Tuesday, Mr Stoltenburg also noted NATO’s record in helping to strengthen the Ukrainian military:
“We support the Ukrainian armed forces in different ways with command and control, with cyber.
"Some allies also provide training in different areas. NATO help them to strengthen their naval capability.”
British soldiers are among those providing the training; since 2015 the British Armed Forces have trained 9,500 Ukrainian personnel.
Soldiers from 3rd Battalion The Rifles were in Ukraine as recently as last week to put local soldiers through their paces as part of Operation Orbital.