Washington: Russia’s alleged cyber-attacks on US political organizations — hacking which the intelligence community concluded amounted to meddling in the US election — were an “act of war,” senior US Senator John McCain said Wednesday.

“It’s an act of war,” McCain, a hawkish Republican and critic of the Kremlin, told reporters in the US Capitol.

“If you try to destroy the fundamentals of democracy, then you have destroyed a nation.”

McCain modulated by insisting there are “gradients” to acts of war.

“I’m not saying it’s an atomic attack. I’m just saying that when you attack a nation’s fundamental structure, which they are doing, then it’s an act of war.”

McCain has been a staunch critic of Moscow, insisting Washington must hit President Vladimir Putin’s government with harder sanctions than the ones President Barack Obama’s administration announced last week for Russia’s role in US election-related hacking.

He has also been critical of US President-elect Donald Trump, who has repeatedly cast doubt over intelligence community conclusions about the cyber-attacks.

Hackers obtained thousands of emails and documents from the computers of the Democratic National Committee and from Hillary Clinton’s campaign chief, which were published by WikiLeaks in the weeks ahead of the November 8 presidential election.

Some of the documents were embarrassing to the Clinton campaign and analysts say they likely contributed to Trump’s victory.

McCain, the 2008 Republican presidential nominee who lost to Obama, traveled last week on a congressional trip to Ukraine.

He said a key takeaway from his visit was that Ukrainian officials “want an American presence” as a bulwark against Russia.

“They’re scared to death of Putin. And they’re scared to death of us abandoning them,” McCain said Wednesday.

On Thursday, the Senate Armed Services Committee, led by McCain, holds the first public hearing in Congress on the hacking, with witnesses including Director of National Intelligence James Clapper and National Security Agency Director Michael Rogers.