Image copyright Reuters Image caption Some social media sites used across the rest of the world are blocked in China

The director of China's internet regulator has admitted that some foreign websites cannot be visited but denied shutting them down.

Lu Wei, who heads the State Internet Information Office, also said his department was planning to strengthen measures to "govern the internet".

Twitter, Facebook and the New York Times are not accessible in China.

The BBC's English-language website was blocked earlier this month, joining the BBC Chinese site.

Mr Lu was responding to queries at a press conference on the forthcoming World Internet Conference due to be held in Zhejiang province.

'Specifying behaviour'

Asked by a reporter why sites such as Facebook had been shut down, Mr Lu replied: "I have never used any of these websites so I don't know if they have been shut down. But as for situations where some sites become inaccessible, I think it is possible.

"We have never shut down any foreign sites. Your website is on your home soil. How can I go over to your home and shut it down?"

Mr Lu however added that while China was "hospitable", it could also "choose who can come to our home and be our guest".

"I can't change who you are but I have the power to choose my friends," he said. "I wish that all who come to China will be our real friends."

Mr Lu added that his department's measures were "meant to protect China's national security and China's consumers".

"We are going to further strengthen our rule of law, our administration, governance and usage of the internet, and use the law to specify behaviour in the online space," he added.

China keeps a tight grip on the internet.

Posts about sensitive topics are routinely scrubbed from the popular micro-blogging service Weibo, as seen during the recent Hong Kong protests.

State media said last year that the government employed more than two million people to monitor web activity.