News Corp companies have been targeted again by Chinese hackers, Rupert Murdoch says.

"Chinese still hacking us, or were over the weekend," the News Corp chairman and chief executive tweeted on Wednesday.

It comes after the Wall Street Journal claimed last week that it had been targeted by Chinese hackers "for the apparent purpose of monitoring the newspaper's China coverage".

The Journal's parent company Dow Jones, a unit of News Corp, suggested that Chinese spying on US media has become a "widespread phenomenon".

The New York Times and a number of other US media outlets also claim to have been targeted by hackers in recent months.

Twitter revealed on February 1 that it had been affected by a "sophisticated" cyber attack and that the passwords of about 250,000 users were stolen.

Mr Murdoch did not add to his tweet on Wednesday or specify which News Corp companies had been targeted over the weekend.