Britain and the European Union have imposed sanctions on Alexander Petrov and Ruslan Boshirov, the two Russian military intelligence officers accused of carrying out the Salisbury novichok poisoning, as well as the leadership of the service, the GRU.

Igor Olegovich Kostyukov, the GRU chief, and his deputy, Vladimir Stepanovich Alexseyev, have also been placed on the sanctions list over the first attack using a nerve agent in Europe since the Second World War which targeted Sergei Skripal, a former member of the service and MI6 agent.

The sanctions, the first by the EU as part of punitive measures to combat the use of chemical weapons, also focused on the Syrian regime’s Scientific Studies and Research Centre, naming Tariq Yasmina, Khaled Nasri, Walid Zughaib, Firas Ahmed and Said Said as playing key roles in the use of chemical weapons by President Bashar al-Assad’s forces in the country’s civil war, including on the city of Douma.

All those placed on the list face travel restrictions and having financial assets abroad frozen. It is unclear at the moment whether Donald Trump’s administration in the US will bring in similar measures.

In September last year, Mr Petrov and Mr Borishov were charged by UK authorities with conspiracy to murder Mr Skripal, his attempted murder and those of his daughter Yulia and Nick Bailey, a British police officer who was poisoned trying to help them.

Four months later another Salisbury resident, Dawn Sturgess, died after coming into contact with the nerve agent, which had been put in a perfume bottle, and her partner, Charlie Rowley, had to be given extensive medical treatment.

Theresa May and British government ministers have blamed the Kremlin for the attack. The Russian government has denied any involvement.

Mr Petrov and Mr Borishov, who appeared on a Russian television interview protesting their innocence and claiming they had visited Salisbury as tourists to see the city’s cathedral, remain members of the GRU, according to security sources. There is no evidence that they have travelled outside Russia since their identities were exposed.

The European Council proposed imposing sanctions for the use of chemical weapons in March last year and announced three months later that this should take place “as soon as possible”. Work had been subsequently carried out, say diplomats, to gather further intelligence and evidence on those who would be held culpable.

Foreign secretary Jeremy Hunt said: “Today’s new sanctions deliver on our vow to take tough action against the reckless and irresponsible activities of the Russian military intelligence organisation, the GRU, which put innocent British citizens in serious danger in Salisbury last year.

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“We have also imposed sanctions on individuals and an organisation responsible for the Syrian regime’s abhorrent use of chemical weapons over many years, including in Douma in April 2018.