NATO Secretary-General Mark Rutte has warned that a Russian victory over Ukraine would undermine the dissuasive force of the world’s biggest military alliance and could cost trillions of dollars to restore the organization's credibility.

Russia on Thursday rejected the idea of NATO countries sending peacekeeping troops to Ukraine in the event of a ceasefire in the war with Russia, saying such a move would threaten to cause an "uncontrollable escalation".

Russia is believed to be behind dozens of hybrid attacks, like arson or sabotage, on NATO soil since the Ukraine war started.