Donald Tusk, the president of the European Council, has said that 14 EU countries are to expel Russian diplomats following the poisoning of Sergei Skripal.
Tusk made the announcement after the US said it had expelled 60 Russians and ordered the closure of the Russian Consulate in Seattle, Washington.
Tusk tweeted: "Today 14 EU Member States decided to expel Russian diplomats as direct follow-up to #EUCO discussion last week on #SalisburyAttack.
"Additional measures including further expulsions are not excluded in coming days, weeks."
Boris Johnson also tweeted: "Today's extraordinary international response by our allies stands in history as the largest collective expulsion of Russian intelligence officers ever & will help defend our shared security. Russia cannot break international rules with impunity."
Canada is to expel four Russian diplomats and will not be allowing entry to three more, the nation's foreign minister Chrystia Freeland said.
Lithuania's foreign minister, Linas Linkevicius, tweeted that his country will expel three "Russian intelligence officers operating under diplomatic cover; sanction additional 21 individuals under the Lithuanian Magnitsky Act; ban 23 more from the entrance to LT."
Sarah Sanders, the White House press secretary, also tweeted: "Today President Donald J. Trump ordered the expulsion of dozens of Russian intelligence officers from the United States and the closure of the Russian consulate in Seattle due to its proximity to one of our submarine bases and Boeing.
"The United States takes this action in conjunction with our Nato allies and partners around the world in response to Russia's use of a military-grade chemical weapon on the soil of the United Kingdom, the latest in its ongoing pattern of destabilizing activities around the world."
A White House statement added that this would make the US safer as Russia would have a reduced ability to spy on Americans and the act would "make clear to Russia that its actions have consequences".
Former double agent Skripal was poisoned with a nerve agent in Salisbury alongside his daughter Yulia. Both remain in hospital in a critical condition.