The travel bans and asset freezes also target the head and deputy head of the GRU, the Russian military intelligence unit thought to have orchestrated the attempted assassination in Salisbury in March of last year.
The names of Petrov and Boshirov were proposed by the UK, which has accused the two men of spraying deadly nerve agent Novichok on Skripal’s front door.
Foreign Secretary Jeremy Hunt said in a statement on Monday: “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.
“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.”
The Kremlin has shrugged off the sanctions, saying Britain had still not handed over the evidence it had gathered against the two men and said their guilt had not been proven.
Petrov and Boshirov have denied they were involved in the affair, instead claiming they were on a two-day international jaunt to visit Salisbury Cathedral.
They made the claim in September on the Kremlin-backed RT channel during an interview that was widely mocked after they described the cathedral in a way that mysteriously echoed the building’s Wikipedia page.
They also failed to explain why they spent a large part of a day walking a route that took them to parts of Salisbury with no notable tourist attractions, but which did take them close to the Skripal house.
Since the interview aired, the Bellingcat website has released numerous reports indicating the two men in fact work for the GRU and their real names are Dr Alexander Yevgenyevich Mishkin and Colonel Anatoliy Chepiga.
The biggest hole in the pair’s story is the fact no record of either man exists from before 2009, when passports under their names were issued, which “suggests the two names were likely cover identities for operatives of one of the Russian security services”.
Over the weekend, it emerged a teenage girl was the first person to help Sergei and Yulia Skripral.
Abigail McCourt was with her family when she saw the 66-year-old ex-KGB spy and his daughter collapsed on a bench at The Maltings shopping centre in Salisbury on the afternoon of 4 March last year.
The 16-year-old thought Skripral had suffered a heart attack and alerted her mother Alison, who is an Army colonel and chief nursing officer, and they went to administer first aid.
Skripal and his daughter survived the attack, which Prime Minister Theresa May said had “almost certainly” been approved by the Russian state.
Dawn Sturgess, 44, fell ill in Amesbury months after the incident and died in hospital in July after coming into contact with a perfume bottle believed to have been used in the attack on the Skripals and then discarded.
Her partner, Charlie Rowley, 45, was also exposed to the nerve agent, but was treated and discharged.
The sanctions imposed by the EU also relate to an alleged chemical attack in the Syrian town of Douma on 7 April last year.
Around 40 people died while under attack by forces loyal to President Bashar al-Assad.
The Organisation for the Prohibition of Chemical Weapons, the international body charged with investigating chemical weapons attacks, is yet to file its final report on Douma and has not yet confirmed that a nerve agent was used.
Rescue workers and medics claimed the victims died due to exposure to either a nerve agent or chlorine gas.
Chlorine gas is not a banned chemical weapon due to its widespread use in a number of domestic applications.
The Assad regime has been found responsible for a number of attacks on civilians using nerve agents and chlorine gas.