China has blocked Internet searches for the term "body double" after web users expressed suspicions that convicted murderer Gu Kailai used a stand-in at her court hearings.

Chinese state television on Monday showed a brief clip of Gu, wife of the disgraced former Communist party leader Bo Xilai, standing in the dock as she was convicted and sentenced for the murder of a British businessman.

But her appearance -- looking notably plumper than in earlier photographs that have appeared in foreign media -- sparked suspicions that the woman in court might actually have been someone else.

Some overseas Chinese websites even alleged the person who appeared in court was a woman called Zhao Tianshao, from northern China's Langfang city.

China's censors moved quickly to muzzle the rumours and on Wednesday the term "ti shen", or body double, remained blocked on many popular websites in the country.

A search for the combined terms "ti shen" and "Gu Kailai" on Baidu, the top search engine in China, returned a line saying "part of the search results are not displayed according to relevant laws and policies".

Sina Weibo, a microblogging service similar to Twitter, which is banned in China, blocked any postings that mentioned "ti shen".

It is not the first time that a high-profile defendant has been accused of using a stand-in in China.

In 2009 there were suspicions that the son of a wealthy businessman who ran over and killed a young man had used a stand-in at his trial, after he appeared noticeably heavier than in pictures taken at the scene of the accident.

China's state-run media have stuck to official accounts of the Gu murder case, which brought down her politician husband and rattled the Communist party before a handover of power due to start later this year.