Iran condemned as "unfounded" Wednesday US allegations of "malicious cyber activity" on behalf of its military that triggered a new set of sanctions against Iranian companies and individuals.

Foreign ministry spokesman Nasser Kanani said Iran "categorically dismissed the US government claim that some Iranian individuals and companies have been involved in cyberattacks".

He accused Washington of seeking to "deflect the wave of international criticism towards their policies of unlimited support for the Zionist regime (Israeli) war crimes and genocide in the Gaza Strip".

The US Treasury Department announced the sanctions against four individuals and two companies on Tuesday, adding that the four individuals had also been indicted "for their roles in cyber activity targeting US entities".

"These actors targeted more than a dozen US companies and government entities through cyber operations, including spear phishing and malware attacks," on behalf of Iran's Revolutionary Guards, it alleged.

The United States, Britain and the European Union have all imposed new sanctions against Iran in recent days following its unprecedented April 13-14 attack on Israel in retaliation for a deadly air strike on its consulate in Damascus.