The cyber-security firm that identified the large-scale hacking of US government agencies says it "genuinely impacted" around 50 organisations.

Kevin Mandia, CEO of FireEye, said that while some 18,000 organisations had the malicious code in their networks, it was the 50 who suffered major breaches.

The US Treasury and departments of homeland security, state and defence are known to have been targeted.

US Secretary of State Mike Pompeo has blamed Russia for the hack.

So too have the chairs of the Senate and House of Representatives' intelligence committees.

However, President Trump cast doubt on Russia's role in two tweets on Saturday, hinting instead at Chinese involvement.

Read more: BBC News