Russian warship 'fires warning shot at a British yacht in English Channel'

The Mail reports

Varun Chuni, prosecuting, told the magistrates' court hearing: 'On the morning of June 14, Royal Marines and the National Crime Agency boarded the oil tanker MV Smyrtos, that vessel had entered UK territorial waters without a legitimate flag.

But the BBC

The MoD said the operation happened in international waters as it was more than 12 nautical miles from the UK coast. [1]

So is this an act of state piracy or not?

[1] https://www.bbc.co.uk/news/articles/clyek039l2vo