The European Commission said Saturday it had not found any computer system intrusion following revelations of a massive cyberattack on US government and other networks, but was "analysing the situation".

The EU executive "is aware of the global software supply chain cyber threat" via hacked software supplied by US tech company SolarWinds but " we have not detected any impact on our systems," a spokesman said.

An EU official told AFP that the Commission has "only one instance" of SolarWinds' software in its systems and "it was not impacted by the incident".

Microsoft said Thursday that its anti-virus defences found dozens of networked systems running the software had been compromised, most of them in the US but also in seven other countries including Belgium, home to the European Commission.

The US has blamed Russia for the cyberattack, but Moscow denies involvement.

NATO, which is also headquartered in Belgium, said it, too, was checking its systems, some of which use SolarWinds software, but had found "no evidence of compromise" so far.

SolarWinds said up to 18,000 customers, including government agencies and Fortune 500 companies, had downloaded compromised software updates, allowing hackers to spy on email exchanges.