Image copyright Deng Guilian

A Chinese activist has been detained while investigating alleged workers' rights abuses at a supplier for Ivanka Trump's shoe brand.

Hua Haifeng was working undercover for the US-based China Labor Watch (CLW), which said he had witnessed examples of forced overtime and wage violations.

Two other activists involved in the investigation are missing, CLW said.

The supplier also makes products for other brands including Karl Lagerfeld, Coach and Nine West, it said.

CLW called on US President Trump to press for the release of Mr Hua.

Amnesty International has demanded the release all three activists, saying the two missing are feared to also have been detained.

Image copyright Getty Images Image caption Ivanka Trump shoes made in China are thought to have been among the products manufactured at this factory

"The trio appear to be the latest to fall foul of the Chinese authorities' aggressive campaign against human rights activists who have any ties to overseas organizations, using the pretence of 'national security'," William Nee, China researcher at Amnesty International, said in a statement.

There has been no comment so far from Chinese authorities, the Trump administration or the Ivanka Trump brand.

'I was shocked'

CLW said Mr Hua was detained in Jiangxi province on suspicion of illegally using eavesdropping equipment but that this allegation had "no factual basis".

The group's executive director, Li Qiang, told the BBC the firm Mr Hua had been investigating, Huajian Group, had "violated workers' rights in ways that included: forced overtime, wages lower than China's legal minimum wage, managers' verbal abuse of workers, and violations of women's rights".

In 17 years of investigating Chinese factories it was "the first time any [of] our investigators have been detained under a criminal process," Mr Li said.

Image copyright Getty Images Image caption Coach is said to be another brand produced at the factory

Mr Hua's wife told the BBC she had lost contact with him on 28 May, but then police contacted her on Tuesday to say he was being held.

"I was shocked and freaked out," Deng Guilian said.

"I only know that my husband was investigating a factory based in Ganzhou, Jiangxi province. That factory manufactures US president's daughter's product," she said.

"I think he was detained for that. Police told me that my husband has been detained for illegal monitoring activities."

The other two men - named as Li Zhao and Su Heng - were working undercover at Huajian factories in Dongguan in Guangdong province and in Ganzhou.

China has seen frequent crackdowns on labour rights activists and rights lawyers in recent years, with campaigners being harassed, arrested or jailed.