Britain’s “disinterest” in providing evidence that Moscow had a hand in the poisoning of a former spy leads it to believe that UK agents were behind the nerve-gas attack, Russia has said.

The Russian foreign ministry on Wednesday accused the British government of dragging its feet in the investigation to uncover the motive and “perpetrators” involved in the gassing earlier this month of former Russian agent Sergei Skripal and his daughter Yulia in Salisbury, England.

Britain’s behavior “leads us to the idea of a possible involvement of the British special services. If the Russian side is not provided with convincing evidence to the contrary, we will assume that we are dealing with an attempt on the lives of our fellow citizens as a result of a huge political provocation,” the foreign ministry said.

It said the incident has raised fears that Britain cannot “guarantee the safety of Russian citizens on their territory.”

The accusation comes a day after more than 20 countries and NATO expelled more than 150 Russian diplomats for the poisoning of the Skripals on March 4. The two remain in critical condition.

In Australia, which announced Wednesday it would expel two Russians, the Russian ambassador warned the world is heading to a “Cold War situation.”