BEIJING: Access to the website of the British newspaper, the Guardian, has been blocked in China, the newspaper said on Wednesday, adding that it did not know why.

The websites of the New York Times Co and Bloomberg News have been blocked in China for more than a year after they published reports about the wealth of family members of former Premier Wen Jiabao and President Xi Jinping, respectively.

China's ruling Communist Party, anxious to maintain power and preserve stability, routinely blocks access to foreign news websites it deems inappropriate or politically sensitive.

The Guardian cited an anti-censorship website, greatfire.org, as saying that its website was first blocked on Tuesday.

“The reasons for the Guardian block are unclear — no China-related stories published by the Guardian in the past two days would obviously be perceived as dangerous by the country's leadership,” the newspaper said in an article on its website.

Access to the Guardian, and other blocked websites, is limited to people with virtual private networks (VPNs) that can bypass China's internet blocking mechanism, known as the Great Firewall.

When asked about the Guardian's website being blocked in China, Foreign Ministry spokeswoman Hua Chunying said: “This is the first time I have heard of this.

“I don't understand the situation. You can inquire with China's relevant department,” she said at a daily news briefing.

The Guardian said a Jan 6 report it ran explored tension in China's ethnically diverse and troubled northwestern region of Xinjiang, but added that the newspaper “has covered the subject before without any noticeable fallout”.

The blocking of the Guardian's website comes after the United States expressed concern about China's efforts to restrict the activity of foreign news organisations.

Neither the New York Times Co nor Bloomberg News was given new journalist visas for more than a year.

Foreign journalists from the two media organisations had feared they may have to leave China after the government gave no indication it would grant them their accreditations, a move criticised by US Vice President Joe Biden on a visit to Beijing last month.

But the government in December renewed the press accreditations for journalists from Bloomberg News and several New York Times reporters.

The Chinese-language websites of Thomson Reuters and the Wall Street Journal were blocked in mid-November. The websites became accessible on Dec 25.

Foreign reporters working in China face numerous difficulties, including a lack of access to top officials and harassment, and even violence, when covering sensitive issues such as protests. China says foreign media are granted wide-ranging freedoms.

Bloomberg LP, the news and financial information company, competes with Thomson Reuters.