Russia had nothing to do with a massive global cyber-attack, President Vladimir Putin said Monday, criticising the US intelligence community for creating the original software.

Hundreds of thousands of computers in more than 150 countries have been hit by the ransomware attack, which has been described as the largest-ever of its kind.

It began Friday and struck banks, hospitals and government agencies among a variety of other targets, exploiting known vulnerabilities in older Microsoft computer operating systems.

"As for the source of these threats, Microsoft's leadership stated this directly, they said the source of the virus was the special services of the United States," Putin said.

What Is WannaCry, and Everything Else You Need to Know About It

He was referring to a weekend blog post by Microsoft president Brad Smith stating that the US National Security Agency had developed the code being used in the attack.

It was leaked as part of a document dump, according to researchers.

"A genie let out of a bottle of this kind, especially created by secret services, can then cause damage to its authors and creators," Putin said on the sidelines of an international summit in Beijing.

"This completely doesn't concern Russia."

The US has accused Russia in the past of mounting several cyber-attacks.

Ransomware Cyber-Attacks Fuel Concern About US Vulnerability Disclosures

In March the Justice Department indicted two officials of Russia's Federal Security Service and two criminal hackers whom they allegedly hired to steal data from some 500 million Yahoo user accounts.

While there was "no significant damage" to Russian institutions such as banks and hospitals, Putin said the incident was "worrisome" and warranted immediate talks "on a serious political level".

"There is nothing good in this and calls for concern," he said.

"A protection system from these manifestations needs to be worked out."