BEIJING (Reuters) - Three of China's largest Internet companies have promised the government they will take steps to banish online rumors, state media said on Tuesday, as the ruling Communist Party fights jitters over a tricky leadership transition.

A dispatch by the official Xinhua news agency made no mention of rumors of a foiled coup in Beijing that spread on the Internet in past weeks, after the abrupt ousting of Bo Xilai, a contender for a spot in the new central leadership to be unveiled at a party congress later this year.

But the article was the latest in a series carried by state media lambasting online rumors and those who spread them.

The March 15 ouster of Bo as party chief of the inland city of Chongqing, linked to a scandal involving a senior aide, has shaken the party ahead of the leadership changes.

After Bo was sacked, popular microblogs, including those run by Sina Corp. and Tencent Holdings Ltd, were awash with speculation about a coup.

Xinhua said that both companies, along with top search engine Baidu Inc, would "resolutely support and cooperate with relevant government departments in measures to fight and clear up online rumors".

They would also "earnestly fulfill their responsibility to society, follow the law, increase management of the Internet and adopt effective measures" to guard against rumors.

While the coup rumors were unfounded, their spread and the tightening of Internet controls and warnings to ignore such talk have reflected worries about stability after Bo's fall.

Last week, China's top military newspaper told troops to ignore online rumors.

And in late March, authorities shut 16 Chinese websites and detained six people accused of spreading rumors about unusual military movements and security in the capital.

The rumors fed on speculation about the ousting of Bo over a month after his vice mayor, Wang Lijun, fled to a U.S. consulate, triggering a scandal exposing accusations of infighting and abuses of power.