Amnesty International says dozens of Chinese firms are producing and exporting "tools of torture" to countries with bad human rights records.

More than 130 companies are involved in producing or trading the equipment, typically marketed to law enforcement agencies, up from about 28 companies a decade ago, Amnesty said.

The equipment fuels human rights abuses by law enforcement authorities in African and Southeast Asian states, the group said in a report.

One company, China Xining Import/Export Corporation, which advertises thumb cuffs, restraint chairs and electric stun guns, said in 2012 it had ties to more than 40 African countries, according to Amnesty.

The firm could not be reached for comment.

The rights group worked with the British-based Omega Research Foundation, which researches the trade and the use of military, security and police equipment.

China's Foreign Ministry could not be immediately reached for comment.

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