Western nations have banded together to expel more than 100 Russian diplomats they accused of being spies, punishing Moscow for its alleged poisoning of an ex-intelligence officer in Britain.
President Donald Trump, under constant political heat for his reluctance to challenge Russia, ordered 60 of its diplomats out of the US - all of them spies, the White House said.
The US called it the largest expulsion of Russian spies in American history, and also closed Russia's consulate in Seattle, deeming it a counterintelligence threat.
At least 21 countries have ousted more than 135 Russians, including 23 kicked out earlier by the UK.
The American moves illustrated an increased willingness by Mr Trump's administration to push back on the Kremlin, even as the president steadfastly avoids challenging Russian President Vladimir Putin personally or directly.
Less than a week ago, Mr Trump congratulated Mr Putin for his re-election but did not raise the March 4 spy poisoning, Russia's alleged election-meddling in the US or its own tainted voting process, prompting a backlash even from Mr Trump's fellow Republicans.
In a choreographed show of transatlantic unity, the US and European allies carefully timed their announcements for maximum effect.
Within a few hours, at least 16 European Union nations expelled Russians, with more likely to follow.
Germany, Poland and France each said they planned to boot out four Russian diplomats, the Czech Republic and Lithuania ousted three and Italy two.
Canada also took action, kicking out four Russians and denying three who had applied to enter the country.
The list included nations in Russia's back yard that have perhaps the most at stake.
Ukraine, a non-EU country with its own conflicts with Moscow, was expelling 13 Russians. All three Baltic states said they would make diplomats leave.
Almost all of the countries said publicly that those being expelled were Russians intelligence operatives working under diplomatic cover.
Moscow threatened tit-for-tat retaliation, suggesting it would kick out an equal number of foreign diplomats.
Russia's Embassy in Washington responded to the Seattle consulate closure by asking its Twitter followers to "vote" which US consulate should be closed in turn: St Petersburg, Yekaterinburg or Vladivostok.
"This is an attempt on the lives of Russian citizens on the territory of Great Britain," Russia's Foreign Ministry said.
"It goes without saying that this unfriendly move by this group of countries will not go unnoticed."
The duelling allegations added to a serious escalation of tension and distrust between Russia and the West, intensified most recently by a bizarre poisoning this month that evoked the spy rivalries of the Cold War.
Britain has accused Moscow of using the Soviet-developed nerve agent Novichok to poison Sergei Skripal, a former Russian military intelligence officer convicted of spying for the UK, and his daughter Yulia on British soil.
The two remain in critical condition and unconscious. The US, France and Germany have agreed it is highly likely Russia was responsible.
Russia has denied responsibility, while accusing Britain of leading a global charge against it without proof.