NATO canceled the accreditation of eight members of the Russian mission on Wednesday, saying they were "undeclared Russian intelligence officers."
A NATO official said the alliance reduced the number of positions Russia can accredit from 20 to 10.
Noting that NATO's policy to Russia remains consistent, the official said: "We have strengthened our deterrence and defense in response to Russia's aggressive actions, while at the same time we remain open for a meaningful dialogue."
According to Russian news agency Interfax, Leonid Slutsky, head of the Russian lower house of parliament's international affairs committee, said: "Moscow would retaliate."
Relations between NATO and Russia have been strained, especially after the country’s illegal annexation of Crimea in 2014 and the alleged poisoning of Russian opposition figure Alexei Navalny last year.
NATO canceled the accreditation of seven Russian officials in 2018 for the poisoning of former Russian spy Sergei Skripal./aa