Classified NSA (National Security Agency) documents leaked by Edward Snowden, a former agency contractor, appear to show that the US pried into servers at the Shenzhen headquarters of Huawei.

Huawei, which has long been the subject of security suspicion (particularly in the US), said in a statement, quoted by the Financial Times, that 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”.

According to the leaked documents, as reported by the New York Times (NYT) and Der Spiegel over the weekend, NSA officials also monitored communications of the firm’s top executives

The goals of the Huawei surveillance operation – code-named “Shotgiant” – were wide-ranging.

One aim, according to a NSA document dated 2010, was to find links between Huawei and the People’s Liberation Army (PLA). Ren Zhengfei, Huawei’s founder, served as an engineer in the PLA, which has caused concern in some political quarters in the West.

Another “Shotgiant” goal, according to the NYT report, was to “exploit” Huawei technology. So, when countries bought equipment from Chinese supplier, the NSA could probe the kit to conduct surveillance.

“Many of our targets communicate over Huawei-produced products,” an NSA document is quoted as saying. “We want to make sure that we know how to exploit these products,” it added, to “gain access to networks of interest [around the world]”.

Caitlin Hayden, a White House spokeswoman, quoted by NYT, said: “We do not give intelligence we collect to US companies to enhance their international competitiveness or increase their bottom line. Many countries cannot say the same.”

Hong Lei, a China foreign ministry spokesman, quoted by Reuters, said China was “extremely concerned” about the spying allegations.

“Recently, the  international media has put out a lot of reports about the eavesdropping, surveillance and stealing of secrets by the United States of other countries, including China,” he told a regular briefing.

“China has already lodged many complaints with the United States about this. We demand that the United States makes a clear explanation and stop such acts.”

The revelations over the weekend by the NYT and Der Spiegel – that NSA infiltrated Huawei’s servers – comes against a backdrop of persistent finger-pointing by some US politicians that Huawei (and fellow Chinese supplier ZTE) pose a threat to American security.

In October 2012 the US House of Representatives published a report about the supposed threat that Huawei (and ZTE) posed, citing opaque governance structures and links to China’s Communist Party. Both Huawei and ZTE immediately hit back at the report, claiming there was no hard evidence to back up the allegations.

Deputy Huawei chairman, Ken Hu, in a foreword to the Chinese supplier’s recent white paper on cyber security, said any notion that the firm might be involved in government-backed cyber hacking was entirely unfounded.

The US, at least publically, has never given any proof that either Huawei or ZTE pose a security threat.