A Russian frigate fired warning shots to divert a UK-flagged civilian yacht near British territorial waters on Tuesday, according to Russia's Defence Ministry.
The ministry said the crew of the frigate Admiral Grigorovich spotted a yacht travelling on a course that risked collision with the ship.
After repeated attempts to establish radio contact failed, the frigate fired warning shots, including small arms fire, ahead of the yacht, the ministry said. It said the yacht then altered course and moved away.
Britain's Ministry of Defence said it was investigating reports of an incident in the Channel.
Russia said the shots were fired when the vessels were 150 metres (164 yards) apart while a source familiar with the incident said they were separated by approximately 457 metres (500 yards).
The incident took place in the Channel about 20 nautical miles south of the Isle of Wight, outside UK territorial waters, and no injuries were reported, according to the source familiar with the incident.
The Russian frigate was being monitored by a Royal Navy vessel at the time, the source said.
In April, the Admiral Grigorovich escorted tankers carrying Russian oil through the Channel.
The Russian ministry said the crew on Tuesday acted in accordance with international maritime rules and took all necessary measures to prevent an incident.
On Sunday, British commandos boarded and intercepted a sanctioned Russian "shadow fleet" oil tanker in the Channel, leading for the first time an operation to disrupt the oil revenue that helps fund Russia's war in Ukraine.
The source said Tuesday's event was not viewed as being linked to that operation and was being treated as an isolated incident.
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