"As we approached, they gave out five blasts on their horn. Which means 'have you seen us?'. We immediately turned two degrees to port, so they could see we made a deliberate change of course, which meant we had seen them.

Direct quote from one of the people on the boat.

"After the distance had closed to 150m, the frigate's commander decided to fire warning shots across the vessel’s bow using small arms,” the ministry said. The yacht then changed course and sailed away, it said.

Not clever on their behalf.

"I was just standing on my course and, as I'm a sailing boat on a course under sail, I've got right of way," he said.

You might have right of way, but they have guns, and a somewhat justified paranoia about small vessels.

… and his gravestone reads: "He would have had right of way."

Jokes aside, remember: Every accusation of the Kremlin is a confession:
If Ukraine had used a civilian ship flying the flag of the UK, to send a russian warship on a visit to the Moskva, it would be a war crime.

It gets better, according to the Russians the vessel was not under way, so the responsibility was entirely on them to avoid a collision.

You might have right of way, but they have guns, and a somewhat justified paranoia about small vessels.

The concept of "stand on" in the international navigation rules is slightly different from right if way as you might apply to a car crash.

I was taught, if you are the "stand on" vessel, you have a duty to maintain steady course and speed. Stay predictable. The last thing the nav rules want is for two vessels to both make course alterations and turn into each other.

I should also add that rule 2 requires all vessels to maneuver when necessary to avoid a collision. Even the stand on vessels.