(Bloomberg) -- The UK summoned the Russian ambassador on Friday, after police earlier charged several men under a new national security law for supporting Russia by carrying out an arson attack against a Ukraine-linked business on British soil.

Britain “remains deeply concerned by allegations of Russian orchestrated malign activity on UK soil, as well as the wider reported pattern of behavior we are witnessing on the part of the Russian Federation to sponsor such activity on the territory of other, sovereign states,” the Foreign Office said in a statement.

The summons and the charges open up a new front in the UK’s dire diplomatic relationship with Russia. Foreign Secretary David Cameron said he was “deeply concerned” by the allegations.

The Foreign Office didn’t explicitly link the summons to the earlier arrests of several British men, who the Crown Prosecution Service said were charged with offenses “in order to benefit Russia” by conducting “hostile activity in the UK.” 

“We call for an immediate cessation of this activity and we will continue to work with our allies to deter and defend against the full spectrum of threats that emanate from Russia,” the Foreign Office said.

The UK has worked with the US in recent weeks to step up sanctions enforcement of Russian activities, including sweeping restrictions announced two weeks ago on trading aluminum, copper and nickel mined in the country. The allies are also reviewing more than $20 billion of cryptocurrency transactions through a Russia-based virtual exchange, Bloomberg reported last month.

The earlier arrests were made under the 2023 National Security Act, which came into force in December, widening the scope for activities that could be charged as threats to national security — including theft of trade secrets and attempts to access certain sites. That gave authorities more powers to prosecute modern forms of spying.

Dylan Earl, 20, is suspected of involvement “in foreign power threat activity” and allegedly planned the arson attack. He has been charged under the National Security Act 2023, marking the first time that the CPS has brought charges under the new legislation.

Paul English, 60, and Nii Mensah, 21, were charged with aggravated arson. Jake Reeves, 22, is accused of agreeing to “accept a material benefit from a foreign intelligence service as well as aggravated arson.” A fifth man, Dmitrijus Paulauska, 22, was charged with having information about terrorist acts.

The men will appear at London’s Old Bailey on May 10.

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