Moscow (CNN) Russia has threatened "retaliatory measures" after the European Union slapped sanctions on senior members of its intelligence agency, the GRU.

"We reserve the right to take retaliatory measures over this unfriendly step," the Russian Foreign Ministry said in a statement on Monday, referring to the sanctions, which include a ban on travel and an asset freeze

Announced Monday, the sanctions target four people over last year's poisoning of ex-Russian double agent Sergei Skripal and his daughter Yulia in the UK.

Two of the men, GRU intelligence officers Alexander Petrov and Ruslan Boshirov, were accused by UK authorities of carrying out the attack using nerve agent Novichok, which they have denied. The EU also sanctioned GRU head Igor Olegovich Kostyukov and his deputy, Vladimir Stepanovich Alexseyev.

Although the Skripals eventually recovered from the 2018 attack, the poison ended up in the hands of another British civilian couple, killing one woman

"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," UK Foreign Secretary Jeremy Hunt said in a statement.

It is the first time the EU has used its new powers to impose sanctions on those connected with chemical weapons use and development, regardless of their nationality and location.

"This decision contributes to the EU's efforts to counter the proliferation and use of chemical weapons which poses a serious threat to international security," the EU's intergovernmental body, the European Council, said in a statement.

Asked to comment on the sanctions on Petrov and Boshirov, Kremlin spokesman Dmitry Peskov rejected the decision.

"They are suspects based on nothing, no evidence has yet been presented," he said on a conference call with reporters on Monday, Russia's state news agency TASS reported.

"We all know a set of already famous photos of these two citizens in the UK," Peskov added, referring to CCTV images of the two men released by British authorities last year. "You also know there are many photographs of Russians in Britain and they are not direct evidence."

Skripal, 66, was found slumped on a bench on March 4, 2018 , along with his daughter, Yulia, after being exposed to Novichok, a military-grade nerve agent.