Bildt: Putin är inblandad i nervgiftsattacken

On 4 March 2018, former Russian military intelligence officer and British spy Sergei Skripal and his daughter Yulia Skripal were poisoned in Salisbury, England, with a Novichok nerve agent, according to official UK sources. As of 26 March 2018, Sergei remained critically ill in hospital and doctors have indicated that he may never fully recover; Yulia, shortly afterwards, was conscious again and able to speak. Detective Sergeant Nick Bailey was also in intensive care after becoming contaminated when he went to Sergei Skripal's house. By 22nd March he had recovered enough to leave the hospital. An additional 46 people sought medical advice after the attack, but none required treatment. In the 1990s, Sergei Skripal was an officer for Russia's Main Intelligence Directorate (GRU) and worked as a double agent for the UK's Secret Intelligence Service from 1995 until his arrest in Moscow in December 2004. He was convicted of high treason and sentenced to 13 years in a penal colony by a Russian court in 2006. He settled in the UK in 2010 following the Illegals Program spy swap. Sergei is a British citizen; Yulia is a Russian citizen, and was visiting her father from Moscow. Later in March, the British government accused Russia of attempted murder and announced a series of punitive measures against Russia, including the expulsion of diplomats. The UK's official assessment of the incident was supported by its allies, which also took the measure of expelling Russian diplomats. Russia denied the accusations and responded in kind to the expulsions and accused Britain of poisoning its former agent Sergei Skripal and his daughter.

Alexander Litvinenko was a former officer of the Russian Federal Security Service (FSB) and KGB, who fled from court prosecution in Russia and received political asylum in the United Kingdom. On 1 November 2006, Litvinenko suddenly fell ill and was hospitalized. He died three weeks later, becoming the first confirmed victim of lethal polonium-210-induced acute radiation syndrome. Litvinenko's allegations about the misdeeds of the FSB and his public deathbed accusations that Russian president Vladimir Putin was behind his unusual malady resulted in worldwide media coverage. Subsequent investigations by British authorities into the circumstances of Litvinenko's death led to serious diplomatic difficulties between the British and Russian governments. During the 2014–2015 trial, the Scotland Yard representative witnessed that "the evidence suggests that the only credible explanation is in one way or another the Russian state is involved in Litvinenko's murder". Another witness stated that Dmitry Kovtun had been speaking openly about the plan to kill Litvinenko that was intended to "set an example" as a punishment for a "traitor". The main suspect in the case, a former officer of the Russian Federal Protective Service (FSO), Andrey Lugovoy, remains in Russia.