One of China's most popular microblogging services has shut several accounts for spreading "malicious" rumours, as Beijing tightens control over the Internet after the ouster of a top leader.

The move followed a broad crackdown on the Internet after rising political star Bo Xilai's downfall in March, sparking a series of online rumours, including one suggesting his supporters had staged a coup.

Chinese Internet giant Sina said late Tuesday it had closed down four "weibo" accounts, China's equivalent to Twitter, including one held by the writer Li Delin, whose postings about military vehicles in Beijing sparked the coup rumours.

A posting by a friend on Wednesday claimed Li had disappeared.

"Recently, some lawbreakers have made use of weibo to without reason fabricate and spread malicious political rumours, producing a bad influence on society," Sina said in an announcement to its more than 300 million users.

It added the four cases had been handed over to the police for handling "under the law".

Other accounts, which did not use real names, included "Yangguang De Yuanshi" who has posted about the Bo scandal and "Guangzhou Wu Guancong" who has called for officials to make public their earnings.

The fourth was "Long Yi Tian-945", Sina said. None of them could be immediately reached for comment.

Bo was removed as the Communist Party chief of Chongqing after his former police chief fled to a US consulate and reportedly demanded political asylum.

Authorities later stripped Bo of his elite party position and placed his wife under investigation for the murder of a British national.

China last month closed 16 websites and made a string of arrests for spreading the coup rumours. Sina itself halted microblog users from commenting on other people's posts for three days along with another operator, Tencent.

The government has also shut two political websites sympathetic to Bo which said they had been ordered to temporarily close after they "maliciously attacked state leaders" and gave "absurd views" about politics.

In its announcement, Sina urged users to obey Chinese law.

"Sina Weibo calls on the vast number of Internet users to respect the law and regulations, do not spread rumours, do not believe rumours," it said.

"On discovering rumours, promptly report them to maintain the healthy Internet environment and good social order."

China has closed 42 websites and deleted more than 210,000 Internet posts since mid-March in the crackdown on online rumours, state media said earlier this month.

The country, which has the world's largest online population at more than half a billion, has for years kept a tight grip on the Internet, censoring content it deems sensitive.

But the rise of microblogs has posed a new challenge, given their vast numbers and speed of posting.