Fresh revelations by former CIA employee Edward Snowden have raised concerns that the US National Security Agency (NSA) may have hacked into Hong Kong's key internet exchange, which handles nearly all the Chinese territory's domestic web traffic.

In an interview in Hong Kong's South China Morning Post newspaper published on Thursday, Snowden said the NSA had been hacking computers in Hong Kong and mainland China since 2009. Among those institutions hacked, he said, was the Chinese University of Hong Kong, which houses the Hong Kong Internet Exchange.

Snowden did not mention the exchange, but his comments have raised concerns that it may have been one of the NSA's targets.

"The fact that the Chinese University was hacked was probably a good choice, if it happened it probably would have been a good choice," said Charles Mok, a member of Hong Kong's legislative council and an IT specialist.

"So the fact that the internet exchange with much of the local domestic traffic would have gone through was probably picked as a target."

Snowden's allegations have until now largely focused on the extent to which the NSA was eavesdropping on US citizens. His most recent comments about China and Hong Kong, where he is believed to be in hiding, draw attention to NSA's role in conducting surveillance of foreign countries.

Snowden was quoted as saying he believed that the NSA had conducted more than 61,000 hacking operations globally. "We hack network backbones - like huge Internet routers, basically - that give us access to the communications of hundreds of thousands of computers without having to hack every single one," the Post quoted him as saying.

The Hong Kong Internet Exchange is one of dozens of Internet Exchange Points, or IXPs, around the globe handling domestic traffic between local service providers and some regional traffic. Such exchanges remove the need for such traffic to take lengthy detours via overseas servers.

The exchange was set up in the mid 1990s and is still run by the university. The university said in a statement that it closely monitored the exchange and had not detected any form of hacking to the network.

Journalists visiting the facility on Thursday, however, were able to walk through an access-restricted door into a "central computer room" with racks of servers without being challenged.

Cathy Huang, an analyst at Frost and Sullivan in Singapore, said that Hong Kong may be especially vulnerable to eavesdropping since its laissez faire economy left it lagging countries like Japan and Australia in setting and enforcing regulations on internet security.

"Hong Kong is quite an open economy and therefore, the government doesn't have many stringent regulations to ensure organizations devote enough resources into Internet security," she said.

Some security experts, however, said that gaining undetected and continuous access to the exchange and placing eavesdropping software or hardware would be hard.

According to people familiar with the operations of the facility, it would be extremely difficult for an unauthorised organisation to insert equipment into the facility without the knowledge of the exchange's administrators.

Mok, the legislative council member, said after talking to administrators at the exchange that any large-scale eavesdropping would have been noticed.

"Certainly they haven't noticed anything," he said. "If it's very advanced, fine, but they can't be copying everything over. It would be noticed and targeted." - Reuters