The United States on Monday led allies in fierce condemnation of China's "malicious" cyber activity, accusing Beijing of extortion and threatening national security, and promising consequences as it charged four Chinese nationals with hacking.

In comments likely to further strain worsening relations between Washington and Beijing, US Secretary of State Antony Blinken also accused China of being behind the massive Microsoft hack disclosed in March, part of a "pattern of irresponsible, disruptive, and destabilizing behavior in cyberspace, which poses a major threat to our economic and national security."

"(China's) Ministry of State Security (MSS) has fostered an ecosystem of criminal contract hackers who carry out both state-sponsored activities and cybercrime for their own financial gain," Blinken said in a statement.  

Meanwhile the US Department of Justice said four Chinese nationals had been charged with hacking the computers of dozens of companies, universities and government bodies in the United States and abroad between 2011 and 2018.

"As evidenced by the indictment of three MSS officers and one of their contract hackers unsealed by the Department of Justice today, the United States will impose consequences on (Chinese) malicious cyber actors for their irresponsible behavior in cyberspace," Blinken said.

The United States, the European Union, Britain, Australia, Canada, New Zealand, Japan and NATO were united against the threat, a senior US official said.

"The cyberattack on Microsoft Exchange Server by Chinese state-backed groups was a reckless but familiar pattern of behavior," British foreign minister Dominic Raab said in a statement. 

The EU issued a statement condemning China's behavior and urging it to "take all appropriate measures" to clamp down on such activities.

Later on Monday, the US-led alliance was due to announce details of action against China over the alleged cyber misconduct, and to reveal 50 "tactics, techniques and procedures" used by Chinese state-sponsored cyber actors, the senior US official said.

The official said US allies were sharing technical advice on how to confront China.

Not just Russia? 

The Microsoft hack, which exploited flaws in the Microsoft Exchange service, affected at least 30,000 US organizations including local governments as well as organizations worldwide, and was already attributed to an "unusually aggressive" Chinese cyber-espionage campaign.

"Responsible states do not indiscriminately compromise global network security nor knowingly harbor cyber criminals -- let alone sponsor or collaborate with them," Blinken said in his statement.

"These contract hackers cost governments and businesses billions of dollars in stolen intellectual property, ransom payments, and cybersecurity mitigation efforts, all while the MSS had them on its payroll."

Accusations of cyberattacks against the United States have recently focused on Russia, rather than China.

Last week, Washington offered $10 million for information about foreign online extortionists as it stepped up efforts to halt the sharp rise in ransomware attacks.

US officials say that many of the attacks originate in Russia, although they have debated to what extent there is state involvement. Russia denies responsibility.

This year has seen a slew of prominent ransomware strikes that have disrupted a major US pipeline, a meat processor and the software firm Kaseya, which affected 1,500 businesses.

Some $350 million was paid to malicious cyber actors last year, a spike of 300 percent from 2019, according to the Department of Homeland Security.

"The US and our allies and partners are not ruling out further actions to hold (China) accountable," the US official said, adding that it was the first time NATO had condemned Chinese cyber activity.

"We're putting forward a common cyber approach with our allies, and laying down clear expectations of how responsible nations behave in cyberspace," the official added.