HONG KONG (REUTERS) - Hong Kong police have charged a democracy activist with misleading police after he claimed he was abducted and assaulted by mainland Chinese agents.

Howard Lam, a veteran yet low-profile member of the city's main opposition group, the Democratic Party, held a press conference last week claiming agents from mainland China forced him into a car in the middle of the city, punched metal staples in the shape of crucifixes into his thighs for being"unpatriotic" and dumped him on a remote beach.

The incident was initially denounced by democracy activists as a shocking breach of Hong Kong's laws and autonomy by the Chinese authorities. But Lam's claims were later challenged after CCTV footage obtained by a local news agency, Factwire, showed a masked man with a passing resemblance to Lam walking freely in the district around the time he claimed he had been abducted. Lam has denied the man in the footage is him.

Hong Kong, a former British colony, was returned to Chinese rule in 1997 amid promises that Beijing grant the city a large degree of autonomy and freedom under a so-called one country, two systems arrangement.

Hong Kong police said in a statement issued late on Wednesday (Aug 16) that Lam has been formally charged with misleading police.

Lam had been arrested early on Tuesday. "The statements made by the person and the information we got from our investigation do not match," said acting commissioner of police Lau Yip-shing, in comments carried by Hong Kong's public broadcaster RTHK.

Lam is under police detention and has been hospitalised since Wednesday night.

Anyone convicted of misleading police by giving false information or making a false report could face six months' imprisonment.