The foreign minister of Finland has said that the U.K. and Finland are discussing plans to require third parties to do more to block the Russian shadow oil tanker fleet operating in the Baltic and the English Channel.

Russian-bought oil tankers navigate the Baltic monthly, using opaque ownership structures to circumvent restrictions stemming from Russia’s war on Ukraine. The waters around Finland act as a key choke point for an estimated 100 of these “shadow” tankers.

The Guardian reports that Elina Valtonen said the EU was looking at further sanctions, adding, “What is very important is that the G7 is active in this as well because obviously what the shadow fleet is doing is circumventing the oil price cap.”

Valtonen was in London May 21 to sign a strategic partnership with the U.K. that reflects the growing ties between the two countries, recently cemented by Finland’s decision to join the North Atlantic Treaty Organization(NATO), a move that extends the defense alliance’s borders with Russia by 830 miles. Finland has closed its border with Russia.

Read More: U.S. Asks About 100 Tankers in Russia Oil Cap Violations Probe

A $60 a barrel price cap on Russian oil imposed in December 2022 was designed to deprive insurance from a tanker transporting oil at above the price cap. The aim had been to restrict the flow of revenue to the Russian war machine while at the same time not causing a huge spike in oil prices that could weaken the world economy.

“We are looking at several ways of making life harder for their ships, but also for those countries under whose flags they are operating,” Valtonen said.