Chinese telecoms and Internet giant Huawei condemned the US National Security Agency on Monday after reports revealed the organisation had been secretly tapping the company's networks for years.
The New York Times and Germany's Der Spiegel said on Saturday that the NSA had accessed Huawei's email archive, communications between top company officials, and even the secret source code of some of its products.
The reports were based on documents provided by fugitive NSA contractor Edward Snowden.
"If the actions in the report are true, Huawei condemns such activities that invaded and infiltrated into our internal corporate network and monitored our communications," Roland Sladek, Huawei's vice president for international affairs, said in a statement.
He added that Huawei "disagrees with all activities that threaten the security of networks and is willing to work with all governments, industry stakeholders and customers, in an open and transparent manner, to jointly address the global challenge of network security".
The original intent of the NSA's Operation "Shotgiant" was to search for links between the Shenzhen-based tech giant and the Chinese military, according to a 2010 document cited by the Times.
But the programme's goal eventually grew to include the penetration of Huawei communications products sold to third countries in order to "gain access to networks of interest" across the globe, the paper said.
The New York Times website is blocked in China and the report could not be accessed on the Chinese Internet.
Washington has long seen Huawei as a security threat due to perceived close links to the Chinese government, which the company denies, and both the United States and Australia have barred it from involvement in broadband projects over espionage fears.
The NSA defended its intelligence-gathering operations, which it maintained were focused only on "valid foreign intelligence targets".
In a statement, the NSA did not cite the New York Times or Der Spiegel by name but criticised the "continuous and selective" publication of details on its surveillance methods, arguing that such reports endanger US national security.
It insisted that NSA activities "are focused and specifically deployed against -- and only against -- valid foreign intelligence targets in response to intelligence requirements".
It also pushed back against suggestions by Snowden and others that spy agencies were waging an industrial espionage campaign on behalf of US businesses.
"We do not use foreign intelligence capabilities to steal the trade secrets of foreign companies on behalf of -- or give intelligence we collect to -- US companies" to enhance their competitiveness, the NSA said.