Beijing, China - China has issued a "strong" rebuke to the US on Tuesday, after Washington and two key allies accused Beijing of responsibility for a series of hacks into key democratic institutions.

On Monday, the US accused China of a 14-year-long "prolific global hacking operation" that has been designed to aid China's "economic espionage and foreign intelligence objectives."

Britain and New Zealand also backed up the allegations.

US Deputy Attorney General Lisa Monaco said the campaign involved more than 10,000 emails sent targeting US and foreign-based businesses, politicians, candidates for elected office, and journalists.

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In response, Chinese authorities on Tuesday insisted that China "opposes and cracks down on all forms of cyberattacks," and accused the US of using the Five Eyes spying alliance – which also includes Britain, Australia, Canada, New Zealand – "to compile and disseminate false information about threats from Chinese hackers."

"China firmly opposes this, has made strong démarches with the United States and relevant parties," foreign ministry spokesperson Lin Jian said. Beijing, he warned, "will take necessary measures to safeguard China's legitimate rights and interests."

A unit dubbed APT31 was described it as a "cyberespionage program" run by China's powerful Ministry of State Security out of the central city of Wuhan.

In a statement released by the Treasury, Washington said that "APT 31 has targeted victims in some of America’s most vital critical infrastructure sectors, including the Defense Industrial Base, information technology, and energy sectors."

"APT 31 actors have gained unauthorized access to multiple Defense Industrial Base victims, including a defense contractor that manufactured flight simulators for the US military, a Tennessee-based aerospace and defense contractor, and an Alabama-based aerospace and defense research corporation."

The governments of Britain and New Zealand backed up the accusations, but China hit back with claims of hypocrisy.

"Relevant Chinese cybersecurity agencies have released a series of reports on the US government's cyberattacks against China and other countries, but the US government has always played dumb," Lin said.