New York Times and Wall Street Journal say they are under attack from China

There are growing fears about Chinese cyber attacks on Western media outlets after two of America's largest newspapers said Chinese hackers had infiltrated their computer systems.

Hours after The New York Times (NYT) said Chinese hackers had targeted its computer network over the last four months, The Wall Street Journal (WSJ), owned by Rupert Murdoch's News Corporation, said it too had been the subject of similar attacks.

A statement from Dow Jones & Co, also owned by News Corporation, said: "Evidence shows that infiltration efforts target the monitoring of the Journal's coverage of China." It added that hacking attacks "related to coverage of China is an ongoing issue".

Earlier, the NYT said it had faced repeated hacking attacks as it prepared a story tracing the hidden riches of the family of Wen Jiabao, the country's premier.

The revelations came just weeks after Chinese authorities forced a NYT reporter to leave the country. Two months after the paper's Shanghai bureau chief David Barboza authored the account of the billions amassed by Mr Wen's relatives, Beijing refused to renew a visa for his colleague Chris Buckley.

In a story on its website, the paper said that as Mr Barboza was working on the piece, hackers had broken into its systems and cracked passwords for every employee. They broke into the email accounts of Mr Barboza and the paper's India-based South Asia bureau chief, Jim Yardley, who has previously reported from Beijing.

"Security experts hired by The [New York] Times to detect and block the computer attacks gathered digital evidence that Chinese hackers, using methods that some consultants have associated with the Chinese military in the past, breached The Times' network," the paper said.

Last year, hackers who according to past diplomatic cables released by WikiLeaks were linked to the Chinese military, infiltrated European Union computers, accessing the emails of Herman Van Rompuy, the President of the European Council, according to the Bloomberg news agency.

The attacks on the NYT first came to light when the story on the Wen family's finances, which used public records to estimate that the premier's relatives "have controlled assets worth at least $2.7bn", was published on 25 October. Warned of "consequences" for its investigation, the paper asked AT&T, the telecoms firm which monitors its computer network, to keep an eye out for unusual activity. AT&T detected hacking activity the day the article went up on the NYT website.

China has denied any role in the hacking, with the country's Ministry of National Defence telling the NYT that its laws prohibited "any action including hacking that damages internet security".