BEIJING (AFP) - China said on Sunday that it was "gravely concerned" over cyber attacks by United States government agencies after new allegations that they had snooped on Chinese targets.

Foreign Ministry spokesman Hua Chunying said the latest reports "again proved that China is the victim of cyber attacks, and we have already lodged representations to the US side", according to state news agency Xinhua.

The remarks followed new claims by former US spy Edward Snowden made to Hong Kong's Sunday Morning Post that US spies had hacked the prestigious Tsinghua University in Beijing - home to one of six "network backbones" that route all of mainland China's Internet traffic - and the Hong Kong headquarters of Pacnet, which operates one of the Asia-Pacific region's largest fibre-optic networks.

The former National Security Agency contractor, who arrived in Moscow on Sunday reportedly on his way to Venezuela, also said the US agency was hacking Chinese mobile phone companies to gather data from millions of text messages.

Earlier on Sunday, Xinhua called the US the world's "biggest villain" for IT espionage, after the new allegations emerged.

"These, along with previous allegations, are clearly troubling signs," Xinhua said in a commentary.

"They demonstrate that the United States, which has long been trying to play innocent as a victim of cyber attacks, has turned out to be the biggest villain in our age," it said.

The US and China are both victims of hacking and have to work together on the issue, Xinhua said.

But it stressed: "The ball is now in Washington's court. The US government had better move to allay the concerns of other countries."

In her comments, Ms Hua said that China opposes all forms of cyber attacks.

"We are willing to enhance dialogue and cooperation with the international community in a spirit of mutual respect, to jointly safeguard peace and security in cyberspace," she said.