The ambitious chief of Chongqing in southwestern China, Bo Xilai, ran into a political storm on Wednesday after his deputy mayor went on leave amid unconfirmed rumours of infighting and even an attempted flight to a U.S. consulate by the deputy.

The city administration said the municipality's deputy mayor Wang Lijun took sick leave for overwork. But his abrupt move after years of serving Bo fanned rumours that Wang sought refuge in the U.S. consulate in Chengdu, several hours drive from Chongqing, after a falling out amid a corruption probe.

The speculation about Wang Lijun seeking U.S. protection could not be confirmed. The Chinese Foreign Ministry spokesman Liu Weimin told reporters he had no information about it.

Even if the rumours are untrue, Wang's departure and the speculation it has fanned could hurt Bo, who is widely seen as seeking a spot in the next Communist Party central leadership, to be settled by late 2012. China's poker-laced leaders like to keep their political dramas muted and behind closed doors.

The political commotion also comes ahead of Chinese Vice President Xi Jinping's visit to the United States next week on a trip that will underscore his virtual certainty of succeeding Hu Jintao as top leader from late 2012.

This will be a big blow to Bo Xilai, because Wang was instrumental in his anti-organised crime campaign, and that was instrumental in building Bo's appeal in public opinion and even among officials, said Chen Ziming, an independent scholar who studies party politics.

Now the hero of that campaign has turned into a scandal, so at the least that's a blow to Bo's public prestige, said Chen, a former political prisoner who lives in Beijing.

Wang has been the law-and-order hatchet man of Bo, a charismatic politician who has encouraged a revival of socialist culture from the time of Mao Zedong while seeking to transform Chongqing's economy into a model of more equal growth.

MENTAL STRESS

Wang, 52, was reassigned last week from overseeing public security to education, environmental protection and other areas.

It is understood that Deputy Mayor Wang Lijun, who has suffered overwork and immense mental stress for a long time, is seriously indisposed physically. He is currently undergoing a vacation-style therapy, the Chongqing information office said on its microblog.

Many Chinese microblog users scoffed at the statement and speculated that Wang was under investigation for corruption, or that he fell out with Bo. Some speculated that Wang bid for protection at the U.S. consulate in Chengdu in Sichuan province, prompting police to gather around the consulate.

The Chinese Foreign Ministry spokesman Liu said he had no information about increased security around the consulate.

The consulate referred questions to the U.S. Embassy in Beijing, where spokesman Richard Buangan said he was not in a position to comment regarding reported requests for asylum.

I can tell you there was no threat to the (Chengdu) consulate yesterday, and the U.S. government did not request increased security around the compound, Buangan told Reuters.

By late Wednesday, the streets around the consulate were quiet and there appeared to be no more security than usual.

On China's hugely popular Weibo Internet microblogging site, searches in Chinese for Wang Lijun and Chengdu consulate remained unfettered, in an unusual departure from the government's usual censoring of sensitive political discussion.

Searches for Bo Xilai were blocked, but all the names of such senior leaders usually are.

Bo, 62, is widely perceived as hungry for a place in the new lineup of Chinese leaders to be settled in a secretive process that culminates in a Communist Party Congress late in 2012 and a national parliament session in early 2013.

He is also a princeling, one of the sons and daughters of China's founding revolutionary elite.

(Additional reporting by Sui-Lee Wee, Sabrina Mao, Sisi Tang in Hong Kong, Benjamin Kang Lim; Editing by Don Durfee and Sanjeev Miglani)