Russia has announced further measures against UK diplomats while at the same time declaring tit-for-tat expulsions of officials from 23 other countries.
It has told the British ambassador to cut staffing to the size of the Russian mission in the UK.
Moscow has rejected UK accusations that it is behind the nerve agent attack on an ex-spy and his daughter in the UK.
However, some 150 Russians have since been expelled by mainly Western countries.
Russia initially hit back at the UK, but then announced 60 US expulsions. On Friday it called in a string of foreign ambassadors with news that their own countries' measures were being matched.
Sergei Skripal and his daughter Yulia collapsed in Salisbury, England, on 4 March. Mr Skripal remains in a critical but stable condition. Yulia's condition is said to be improving.
UN Secretary General Antonio Guterres on Thursday issued a warning over "a situation that is similar, to a large extent, to what we lived during the Cold War".