Russia will lose one-third of the diplomatic detail to the Russia-NATO Council, after the civilian head of the trans-Atlantic alliance revoked the credentials for seven officials and barred three others.

NATO Secretary General Jens Stoltenberg ordered the 10 officials home in response to the attempted assassination of a former Russian military intelligence officer who was convicted of treason and then released to the United Kingdom in 2010. British Prime Minister Theresa May blamed Russia for the attack, saying the ex-spy was poisoned by “a military-grade nerve agent” developed by the Soviet Union during the Cold War.