Britain on Monday ordered its ports to block any vessels that are Russian-flagged or believed to be registered, owned or controlled by any person connected with Russia as it ratcheted up the pressure on Moscow.
Transport Secretary Grant Shapps said in a letter to all UK ports that further detailed sanctions against Russian shipping were being drawn up following Russia's invasion of Ukraine.
"The maritime sector is fundamental to international trade and we must play our part in restricting Russia's economic interests and holding the Russian government to account," he said in the letter published on Twitter.
Shapps said Russian vessels were no longer allowed to enter UK ports and any vessel thought to be owned, controlled, chartered or operated by any person connected with Russia should be barred.
Any vessel operated by a "designated person" or any vessel flying the Russian flag or registered in Russia must also be blocked.
"We will seek to support UK ports in identifying Russian ships within scope of the above, and will communicate directly with relevant ports when we identify ships bound for UK ports who fall within scope of the above," he said.
Russia, which has described its actions in Ukraine as a "special operation", has already responded in kind to other sanctions such as a UK and EU decision to block Russian planes from using their airspace.
Russian vessels carrying cargoes of energy make regular visits to UK ports.
The Marshall Islands flagged SCF Le Perouse, operated by leading Russian shipping group Sovcomflot, made a visit in January to the southern UK terminal Isle of Grain with a cargo of U.S. LNG before sailing back to the Atlantic, ship tracking data on Eikon showed.
It was unclear what would happen with another Sovcomflot-operated vessel, the Marshall Islands-flagged NS Champion, which was scheduled to arrive in the UK on Tuesday with a cargo of oil.
Ship tracking data showed the vessel was still signaling the UK as its destination and its last reported position on Monday was off the coast of Scotland.
Sovcomflot was among the Russian entities listed by the U.S. Treasury last week as being prohibited from engaging in new equity or debt raising moves with U.S. persons or through the U.S. financial system, that have a maturity of more than 14 days, which shipping sources say will complicate transactions for the Moscow-listed company.
Sovcomflot, which has a UK subsidiary, declined to comment on Monday.
(Reuters - Reporting by Kate Holton and Jonathan Saul; Editing by William Schomberg and Hugh Lawson)