Hong Kong police say they've arrested six men, some with links to triad gangs, following a violent attack on pro-democracy protesters at a subway station over the weekend that saw dozens injured.

Senior police official Chan Tin-chu said the men, aged 24-54, were held for "unlawful assembly" and are being investigated for taking part in the attack late Sunday night. Some of them are villagers, and their occupations range from drivers and hawkers to renovation workers, he said.

"Some of them have triad backgrounds," he said. "I believe that more... will be detained soon. Police will not condone any form of violence."

Police are still investigating the motive for the attack, Chan said, without providing further details on the alleged links to the triads, which refer to powerful organized crime syndicates in Hong Kong. The triads control certain neighborhoods in the city and are believed to have strong political influence.

A gang of white-clad men armed with metal rods and wooden poles beat up anti-government protesters and others inside a subway station in Hong Kong's Yuen Long neighborhood late Sunday, injuring 45 people, including a man who remained in critical condition.

