A Russian fighter jet has made close-range passes for more than 90 minutes near an American warship in the Black Sea amid diplomatic tensions between the US and Russia over Ukraine.
Pentagon said on Monday that the Russian Fencer made 12 passes and flew within 900 metres of the destroyer USS Donald Cook on Saturday at about 150 metres above sea level.
"This provocative and unprofessional Russian action is inconsistent with international protocols and previous agreements on the professional interaction between out militaries," Army Colonel Steve Warren, a Pentagon spokesman, said.
The fighter appeared to be unarmed and never was in danger of coming in contact with the ship, said the officials, but it did not respond to radio queries and warnings used by the US warship.
The passes ended without incident.
Warren reported that a second Russian fighter jet was also involved, but it flew at a higher altitude and was not a concern.
A Russian Navy ship, a frigate, has also been shadowing the US warship, remainining within visual distance, but not close enough to be unsafe, according to another US military official who was not authorised to discuss the incident publicly so spoke on condition of anonymity.
The USS Donald Cook, that is now in port at Romania's Constanta, has been conducting routine operations in international waters east of the country.
The ship, which carries helicopters, was deployed to the Black Sea on April 10, in the wake of the Russian military takeover of Ukraine's Crimea region in an effort to reassure US allies and partners in the region.
Romanian President Traian Basescu visited the ship on Monday and said a second US navy warship – a frigate from the Navy's Sixth Fleet in the Mediterranean Sea – is also heading to the Black Sea.
"My visit to the ship is symbolic, which first of all shows our respect to our NATO allies' reaction who have strengthened their presence in the Black Sea after Russia's annexation of Crimea," said Basescu, who is a former ship captain.
He said the Russians "had created a circle of fire around the Black Sea".
The US frigate, which has not yet been identified, is expected to arrive in the Black Sea in the next two weeks.
According to a US military official, the frigate is likely to replace the USS Donald Cook, which is expected to return to the Mediterranean Sea.