"The decision to withdraw the accreditation of eight members of the Russian delegation to NATO was done based on intelligence because these are undeclared Russian intelligence officers," Stoltenberg said.

"We have seen an increase in Russian malign activities, at least in Europe and therefore we need to act."

The NATO chief said that the decision to kick out the Russian representatives was not "linked to any particular event" -- but gave no more details over the move.

NATO announced Wednesday it had decided to strip the "undeclared Russian intelligence officers" of official accreditation to the alliance and halve the size of the Russian delegation to 10.

Stoltenberg reiterated that the "relationship between NATO and Russia is at its lowest point since the end of the Cold War. And that's because of the Russian behaviour."

Ties between the West and Moscow have slumped in recent years since the Kremlin's 2014 annexation of Crimea and over its involvement in the conflict in eastern Ukraine.

Russia has long had an observer mission to NATO as part of a two-decade-old NATO-Russia Council meant to promote cooperation in common security areas, but it is not a member of the US-led Alliance.

The Russian mission has been downsized once before, when seven of its members were ejected after the 2018 poisoning by the Novichok nerve agent on a Russian former double agent, Sergei Skripal, and his daughter in Britain. Accreditation applications by another three Russian diplomats were denied.

Meetings of a NATO-Russia council have not been held since 2019 against the backdrop of the heightened tensions.

"We are ready to engage in meaningful dialogue with with Russia, and we are ready also to convene a NATO-Russia Council meeting," Stoltenberg said.

"We have actually invited Russia for a long time. So far, Russia has not responded positively."

Sky News reported that NATO's decision came after information was revealed in April about fatal explosions at a Czech ammunition depot in 2014 that Prague says involved two Russian spies -- identified as allegedly implicated in the Skripal poisoning.

That Czech Republic-Russia incident led to the mutual expulsion of dozens of EU and Russian diplomats and other embassy staff.