US President Joe Biden has announced new sanctions on the Russian government and the expulsion of 10 diplomats in retaliation for hacking and election interference.

Mr Biden said Russia’s efforts to undermine free elections in the US were an “unusual and extraordinary” threat to security.

The actions represent the first retaliatory measures announced against the Kremlin for both interference in last year’s presidential election and the hacking of federal agencies, familiarly known as the SolarWinds breach.

In that intrusion, Russian cyber criminals are believed to have infected widely-used software with malicious code, enabling them to access the networks of at least nine agencies in what US officials believe was an intelligence-gathering operation aimed at mining government secrets.

FILE - In this March 10, 2011, file photo, then-Vice President Joe Biden, left, shakes hands with Russian Prime Minister Vladimir Putin in Moscow, Russia. Russia and the United States exchanged documents Tuesday Jan. 26, 2021, to extend the New START nuclear treaty, their last remaining arms control pact, the Kremlin said. The Kremlin readout of a phone call between U.S. President Joe Biden and Russian President Vladimir Putin said they voiced satisfaction with the move. (AP Photo/Alexander Zeml
Image: Presidents Biden and Putin met in March 2011 – but relations have now soured dramatically

Besides that hack, US officials last month alleged that Russian President Vladimir Putin authorised influence operations to help Donald Trump in his unsuccessful bid for re-election as president, though there is no evidence Russia or anyone else changed votes or manipulated the outcome.

The measures announced on Thursday include sanctions on six Russian companies that support the country’s cyber activities, in addition to sanctions on 32 individuals and entities accused of attempting to interfere in last year’s presidential election, including by spreading disinformation.

The 10 diplomats being expelled include representatives of Russian intelligence services, the White House said.