Chinese agents allegedly abducted, beat and stapled a Hong-Kong pro-democracy activist because he was planning to send a signed photo of Lionel Messi to a widow of a Noble peace prize laureate.

Howard Lam, a member of Hong Kong's Democratic Party, said on Friday (11 August) that he was kidnapped from the streets on Thursday and was forcefully made to smell something that left him unconscious.

He also said that when he gained consciousness after being hit by a hard object, he found himself blindfolded.

His abductors, who spoke Mandarin – China's national language, interrogated about his objective to send a picture of the Barcelona footballer Messi to Liu Xia, the widow of Nobel peace prize laureate Liu Xiaobo. They also beat him and stapled his legs, Lam later told at a press conference.

"A man asked if I knew Liu Xia," the activist said.

"The man also said: 'Are you a Christian? Do you know how to love the country and the religion? ... I'll give you some crosses,' he said, and then he stapled my legs," Lam said while showing his legs full of at least 20 staples on them to reporters.

He added that his ordeal lasted almost nine hours before the abductors dumped him on a beach in the territory's remote Sai Kung district at midnight on Friday.

Reports say the Noble laureate Liu, who died from cancer while in custody in July, wrote to Barcelona to ask for a signed photo of Messi because he thought it would make him happy. But he died before receiving it.

So Lam decided to hand it over to Liu's wife. The pro-democracy activist also said that before his abduction, he received a phone call from a mainland acquaintance on Monday, warning him not to give Xia the postcard.

"He warned that I'd pay if I ignored the warning," the activist said.

Meanwhile, after receiving the complaint from the activist, Hong Kong police has started their investigation. Chief Executive Carrie Lam Cheng Yuet-ngor's office said a police investigation was underway.

"We appeal to the person to fully cooperate with the investigation. Without any evidence and factual details, it is not appropriate to raise any speculation or make accusations," it said.

The Democratic Party has defended the activist's version and said it saw no reason to doubt his story. The lawmaker Lam Cheuk-ting called it a serious violation of the "one country, two systems" policy.

"The government needs to tell us if Hong Kong residents still enjoy freedom from fear and abduction," he added.

The former British colony was returned to China under the "one country, two systems" agreement, while having its own independent legal system in 1997. Hong Kong's pro-democracy campaigners claim that Beijing's interference in their political system has hampered progress towards its autonomy.