China has closed 42 websites and deleted more than 210,000 posts since mid-March in a crackdown on online "rumours", state media said Thursday, as a major political scandal rocked the country.

The announcement on the official Xinhua news agency came as Chinese authorities ramped up efforts to control online speculation about the purge of a top leader whose wife is suspected in the murder of a British businessman.

It did not refer to this week's dramatic developments surrounding the high-profile and populist former leader Bo Xilai, who was sacked as Chongqing party secretary last month.

But China's weibos -- microblogs similar to Twitter that have taken the country by storm -- have buzzed with speculation about Bo's suspension from the powerful 25-member Politburo and the investigation of his wife for murder.

"Actions of creating and spreading rumours via the Internet disrupt public order and undermine social stability, and will never be tolerated," the report quoted Liu Zhengrong, an official with the State Internet Information Office, which controls the web, as saying.

Bo had been tipped to join an elite group of leaders who effectively run China later this year, and his downfall is the biggest drama to hit the Communist Party in years.

China has the world's largest online population with more than half a billion users, posing huge challenges to the government's efforts to control the information its people are able to access.

Authorities have stepped up their efforts to censor sensitive information amid fears of political instability ahead of a generational transfer of power due to take place later this year.

Last month, two leftist political websites said they had been ordered to shut down for a month for "rectification" after they had "maliciously attacked state leaders" and given "absurd views" about politics.

The latest announcement of site closures came after China said last month it had shut down websites, made a string of arrests and punished two popular microblogs after rumours of a coup that followed Bo's sacking.

Authorities closed 16 websites for spreading rumours of "military vehicles entering Beijing and something wrong going on in Beijing", Xinhua said at the time.

Police arrested six people and the country's two most popular microblogs introduced posting restrictions for three days after a surge in online rumours about a coup led by China's security chief Zhou Yongkang.

In an editorial, the People's Daily, the mouthpiece of the Communist Party, pledged to punish those responsible for the "lies and speculation", but the crackdown drew swift condemnation online.