Russia's defence ministry has accused British navy personnel of blowing up the Nord Stream gas pipelines last month.
On Saturday, the UK hit back at the claim and said it was "false and designed to distract from Russian military failures in Ukraine".
Russia did not give evidence for its claim that a leading Nato member had sabotaged critical Russian infrastructure.
The Russian ministry also accused "British specialists" from the same unit of directing Ukrainian drone attacks on Russian ships in Crimea earlier on Saturday.
It said the attacks were largely repelled by Russian forces, with minor damage to a Russian minesweeper.
"According to available information, representatives of this unit of the British Navy took part in the planning, provision and implementation of a terrorist attack in the Baltic Sea on September 26 this year - blowing up the Nord Stream 1 and Nord Stream 2 gas pipelines," the ministry said.
The UK has denied the claim.
"To detract from their disastrous handling of the illegal invasion of Ukraine, the Russian Ministry of Defence is resorting to peddling false claims of an epic scale," it said.
"This invented story, says more about arguments going on inside the Russian government than it does about the West."
Russia has previously blamed the West for the explosions that ruptured the Russian-built Nord Stream 1 and Nord Stream 2 pipelines on the bed of the Baltic Sea.
But it had not previously given specific details of who it thinks was responsible for the damage to the pipelines, previously the largest routes for Russian gas supplies to Europe.
A sharp drop in pressure on both pipelines was registered on September 26 and seismologists detected explosions, triggering a wave of speculation about sabotage to one of Russia's most important energy corridors.
New underwater footage shows Nord Stream pipeline damage
Sweden and Denmark have both concluded that four leaks on Nord Stream 1 and 2 were caused by explosions, but have not said who might be responsible.
Nato Secretary General Jens Stoltenberg has called the damage an act of sabotage.
Sweden has ordered additional investigations to be carried out into the damage done to the pipelines, the prosecutor in charge of the case said.
The Kremlin has repeatedly said allegations of Russian responsibility for the damage were "stupid" and Russian officials have said Washington had a motive as it wants to sell more liquefied natural gas to Europe.
The United States has also denied involvement.
