Obama expels 35 Russian diplomats over election hacking
They have been given 72 hours to leave the country
President Barack Obama has sanctioned Russian intelligence services and their top officials, kicked out 35 Russian officials and closed down two Russian-owned compounds in the US in a sweeping response to election hacking.
It was the strongest action the Obama administration has taken to date to retaliate for a cyber attack.
"All Americans should be alarmed by Russia's actions," Mr Obama said in a statement released while he was on holiday in Hawaii.
He added: "Such activities have consequences."
The Kremlin responded to the move and said that an "appropriate" retaliation would be ordered.
The spokesman for Russian President Vladimir Putin said the sanctions would harm relations between Moscow and Washington.
Dmitry Peskov said Putin would order an "appropriate" retaliation to the sanctions, which included the expulsion of 35 diplomats.
In a conference call with reporters, Peskov said Moscow doubted the effectiveness of the measures as the current U.S. presidential administration was stepping down in three weeks.
Mr Obama ordered sanctions against two Russian intelligence services, the GRU and the FSB, plus companies which the US says support the GRU.
The cyber security firm hired by the Democratic National Committee to investigate the theft of its emails determined earlier this year the hacking came from the Fancy Bear group, believed to be affiliated with the GRU, Russia's military intelligence agency.
The president also sanctioned Lt Gen Korobov, the head of the GRU, and three of his deputies.
Other individuals sanctioned include Alexei Belan and Yevgeny Bogachev, two Russian nationals who have been wanted by the FBI for cyber crimes for years.
Mr Obama said the hacking "could only have been directed by the highest levels of the Russian government", a contention the US has used to suggest Russian president Vladimir Putin was personally involved.
Although the White House announced at the same time it was kicking out Russian officials and closing facilities, it said those were responses to other troubling Russian behaviour: harassment of US diplomats by Russian personnel and police.
The 35 Russian diplomats being kicked out are intelligence operatives, Mr Obama said.
The state department said they were being declared "persona non grata", and they were given 72 hours to leave the country.
The two compounds being closed down are recreational facilities owned by Russia's government, one in Maryland and one in New York, the US said.
The White House said Russia had been notified that it would be denied access to the sites starting at noon on Friday.
Russian officials have denied the Obama administration's accusation that the Russian government was involved at the highest levels in trying to influence the US presidential election.
US intelligence agencies concluded that Russia's goal was to help Donald Trump win - an assessment Mr Trump has dismissed as ridiculous.
The move puts the president-elect in the position of having to decide whether to roll back the measures once in office.
U.S. House of Representatives Speaker Paul Ryan said on Thursday Russia "has consistently sought to undermine" U.S. interests and sanctions imposed by the Obama administration on Russia were overdue.
"While today's action by the administration is overdue, it is an appropriate way to end eight years of failed policy with Russia," Ryan said in a statement. "And it serves as a prime example of this administration's ineffective foreign policy that has left America weaker in the eyes of the world."
Additional reporting by Reuters.