Singapore, which vies with Hong Kong as Asia's pre-eminent financial centre, tightly restricts public demonstrations and does not allow protests over political situations in other countries.

Hong Kong has been gripped by months of often violent protests against mainland China's perceived growing influence over the semi-autonomous city.

Police questioned Alex Yeung, a Hong Kong resident, for allegedly organising a "gathering" on Oct. 11 at the Kimoto Gastro Bar in the financial district, where guests were invited to share their views on unrest in Hong Kong.

The event later shifted to a public promenade overlooking the glitzy Marina Bay, the police said.

"Currently, Yeung's passport has been impounded while he is assisting the Police with ongoing investigations. He is, however, neither arrested nor in Police custody, and is free to go about his activities within Singapore," the statement said.

Nicholas Narayanan, Yeung's lawyer, said his client couldn't comment due to the ongoing police investigation.

"Our client is fully co-operating with the police at this time," Narayanan said in a statement.

Singapore is closely watching the developments in Hong Kong to avoid suffering similar "deep social angst", Prime Minister Lee Hsien Loong said last month.

Lee, who has criticised the Hong Kong protesters, said Singapore would be "finished" if it went through similar unrest.

(Reporting by Aradhana Aravindan; Writing by Joe Brock; Editing by Alex Richardson)