The Russian military says it forced a British ship out of its territorial waters near the Crimean Peninsula on Wednesday, using bombs and gunfire as warning, but London disputed the account and argued that it was in "Ukrainian territorial waters."
According to a TASS agency report citing Russia's Defence Ministry, weapons were launched after the British Navy's HMS Defender crossed 3 kilometres inside Russian territory in the Black Sea.
A border guard ship fired the warning shots while an SU-24 bomber dropped several bombs, prompting the British vessel to turn around and leave the Russian waters, the ministry said.
The British defence attache in Moscow has been summoned regarding the incident, TASS reported.
But Britain's Ministry of Defence tweeted later that no warning shots were fired at the HMS Defender.
"No warning shots have been fired at HMS Defender," read a tweet. "The Royal Navy ship is conducting innocent passage through Ukrainian territorial waters in accordance with international law."
Moscow claimed control of the Crimean Peninsula in 2014 as Ukrainian forces battled separatists who were backed by Russia. But most Western countries have never acknowledged the annexation.
Neither side reported injuries amid the incident.
Ukrainian Foreign Minister Dmytro Kuleba said the incident was proof of "the aggressive and provocative policies of the Russian Federation in the Black Sea and the Sea of Azov" and called for NATO members to cooperate with Ukraine in the region.
"The occupation and militarization of the Crimea is turning into a steady threat for Ukraine and its allies."
Yuri Shvitkin, the deputy head of the Defence Committee in Russia's legislature, said the country would repulse all attempts to intrude upon the country's borders.
He argued that Russian forces acted in accordance with international law during the incident and that all steps were taken to prevent violence.
It's believed that the British ship is supposed to be participating in international military manoeuvres organized by the US. Russia and its allies have warned other countries not to conduct such exercises in the Black Sea, saying they increase the risk of "unexpected incidents."
The military exercises, dubbed Sea Breeze, are due to start on Monday with 32 countries on six continents sending 5,000 soldiers, 32 ships, 40 aircraft and 18 teams of special operations troops and divers. The exercise is conducted annually, but this is the biggest one so far. This year, it is based in Ukraine.
Recent Russian troop movements on Ukraine's east border had raised fears of another Russian military intervention like the one that resulted in Crimea being taken in 2014. Large parts of eastern Ukraine also remain under the control of the Russian-backed rebels.