"We state the strengthening of Russia in the Black Sea after the illegal annexation of Crimea," RIA Novosti quoted Stoltenberg as saying at a joint press conference in Brussels with Ukrainian Prime Minister Denis Shmygal.
He noted that we are talking, in particular, about strengthening the Russian fleet.
The secretary general added that NATO attaches strategic importance to the Black Sea.
Earlier, in the Black Sea, a boat tactical group with the involvement of the naval aviation of the Naval Forces of the Armed Forces of Ukraine, together with an American destroyer and a support ship, conducted joint training of the PASSEX type.
Crimea became a Russian region after a referendum held there in March 2014, in which most residents voted in favor of reunification with Russia.