A man from the central Chinese province of Henan who traveled to Beijing "to ask for justice" on the eve of the 18th Congress of the ruling Communist Party was beaten to death in custody, China Human Rights Defenders charged on Wednesday.

Zhang Yaodong came to the capital with three other petitioners to appeal to the central government.

"Petitioner" is the term for a citizen who invokes an old Chinese imperial tradition of asking the central government for justice after he or she has exhausted all legal pathways at the local and regional levels.

The majority of such complaints are related to forced expropriations, physical mistreatment, deaths of relatives in custody and other cases of corruption.

Zhang and the other three petitioners, CHRD said, arrived in Beijing on Nov. 5 - three days before the meeting of Chinese leaders began - but they were arrested and taken to one of China's clandestine prisons.

The next day, when Zhang was being forced to return to his province, he was assaulted by three unidentified men after, apparently, he refused to give them his cell phone, CHRD said.

The organization says that the attackers did not take Zhang to the hospital until after he had died from the beating they administered to him.

"This is the most brutal act registered amid the oppressive climate that surrounded the Party Congress," said CHRD.

The atmosphere surrounding the Party Congress was also emphasized by Amnesty International, which said that at least 130 people have been arrested or subjected to various forms of restrictive measures since September. EFE