The United States owes China an explanation about its hacking activities and should show more sincerity in the future when engaging in cybersecurity cooperation between the two countries, experts in Beijing said.

Washington is now in an awkward position regarding its cybersecurity dispute with Beijing, following revelations by whistle-blower Edward Snowden that the US has been hacking into computers in China for years, Jia Xiudong, a senior researcher of US studies at the China Institute of International Studies, said on Thursday.

Snowden, 29, a technician transferred by a private contractor to a US National Security Agency base in Hawaii, told a Hong Kong newspaper on Wednesday that the NSA had been hacking into computers in Hong Kong and the Chinese mainland since 2009. He has been taking refuge in Hong Kong since May 20.

None of the documents revealed any information about Chinese military systems, he said in an interview with the South China Morning Post.

Jia said what Snowden has exposed fully demonstrates that the US has a double standard on cybersecurity, and "its accusation about China is hypocritical and without evidence".

"When it comes to cybersecurity, what the two countries should do is cooperate and resolve their differences and conflicts through dialogue," Jia said.

China and the US have been engaging in a cybersecurity dispute for months, with the US accusing China of cyberattacks.

At a meeting in California last week, US President Barack Obama pushed President Xi Jinping to do more to address online theft of US intellectual and other property coming from China.

Snowden said he believed there had been more than 61,000 NSA hacking operations globally, with hundreds of targets in Hong Kong and on the mainland.

The targets in Hong Kong include Chinese University of Hong Kong, public officials, businesses and students in the city, according to Snowden.

Foreign Ministry spokeswoman Hua Chunying reiterated at a news conference on Thursday that China has been one of the major victims of cyberattacks. "China strongly advocates cybersecurity," she said.

She also stressed China's position that the international community should have constructive cooperation on maintaining peace, security and cooperation in cyberspace.

Snowden leaked information to the media about PRISM, a top-secret program that collects and analyzes data from Internet users around the world. The leak has led to heated debate about privacy and civil liberty in the US.

General Keith Alexander, NSA chief and chief of US Cyber Command, told Congress on Wednesday that information collected by once-secret US surveillance programs has disrupted dozens of terrorist attacks, The Associated Press reported.

Alexander insisted that the public needs to know more about how the top-secret programs operate amid increasing unease about rampant government snooping and fears that citizens' civil liberties are being trampled.

When asked whether the US had approached China about Snowden's extradition and what Beijing's reaction would be if he applied for asylum in Hong Kong, Hua Chunying said she "has no information to offer".

Snowden said, "I have had many opportunities to flee Hong Kong, but I would rather stay and fight the United States government in the courts, because I have faith in Hong Kong's rule of law."

According to AP, US law enforcement officials are building a case against him but have yet to bring charges.

Huang Feng, an expert on international criminal law with Beijing Normal University, said the US is fully aware that it's not in an advantageous position to ask for Snowden to be sent back under its agreement with Hong Kong.

"What Snowden has done, according to US law, will fall under offences of betraying state secrets or treason. Neither of these is listed as a crime that can be used for turning over a fugitive," Huang said.

The Hong Kong government said on Thursday that it has received no report of data loss due to hacking of computer systems.

Contact the writers at chengguangjin@chinadaily.com.cn and kahon@chinadailyhk.com