The Microsoft hack affected at least 30,000 organisations globally
China has denied allegations that it carried out a major cyber-attack against tech giant Microsoft.
The US and other Western countries on Monday accused China of hacking Microsoft Exchange - a popular email platform used by companies worldwide.
They said it was part of a broader pattern of "reckless" behaviour that threatened global security.
China says it opposes all forms of cyber-crime, and has called the claims "fabricated".
"The US has mustered its allies to carry out unreasonable criticisms against China on the issue of cybersecurity," foreign ministry spokesman Zhao Lijian told reporters.
The UK, EU, New Zealand and Australia were among those to join the US in accusing Chinese state-sponsored actors of "malicious cyber activity", including the Microsoft hack.
Microsoft's Exchange system powers the email of major corporations, small businesses and public bodies worldwide. The hack affected at least 30,000 organisations.
Microsoft has blamed a Chinese cyber-espionage group for exploiting a vulnerability in Microsoft Exchange - which allowed hackers to remotely access email inboxes.
The group, known as Hafnium, was found by Microsoft's Threat Intelligence Centre to be state-sponsored and operating out of China.
Western security sources believe Hafnium obtained advance knowledge that Microsoft planned to deal with the vulnerability, and so shared it with other China-based groups to exploit it while they could.
The sources say the hack seems to signal a shift from a targeted espionage campaign to a smash-and-grab raid, leading to concerns that Chinese cyber-behaviour is escalating.
The UK Foreign Office said the Chinese government had "ignored repeated calls to end its reckless campaign, instead allowing state-backed actors to increase the scale of their attacks".
US President Joe Biden said the Chinese government may not have been carrying out the attacks itself, but was "protecting those who are doing it. And maybe even accommodating them being able to do it".
The US Department of Justice on Monday announced criminal charges against four hackers linked to China's Ministry of State Security. It said they were connected to a long-term campaign targeting foreign governments and entities in key sectors in a least a dozen countries.
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