Singapore has deported a Hong Kong YouTube star after he organised a small gathering to discuss the protests convulsing his home city in violation of public assembly laws, police said Thursday.

The city-state's elite are increasingly nervous about the unrest in rival financial hub Hong Kong, observers say, as they fear it could inspire demonstrations in the tightly-controlled country where protests are rare.

Police launched a probe after Alex Yeung, a pro-Beijing restaurateur known for his anti-protest tirades on YouTube, organised the gathering last month in a bar with a handful of people, mostly Hong Kongers.

Organising a public assembly without a police permit in Singapore is punishable by a fine of up to Sg$5,000 ($3,700). Repeat offenders can be fined up to Sg$10,000 or jailed for a maximum of six months or both.

But after wrapping up their probe, police decided to give Yeung only a warning and sent him back to Hong Kong.

"Singapore has always been clear that foreigners should not advocate their political causes in Singapore, through public assemblies, and other prohibited means," said a police statement.

In a video posted after police launched a probe, Yeung had accused supporters of the protests of setting him up at the gathering.

Hong Kong has been shaken by nearly six months of increasingly violent demonstrations, with protesters calling for greater democratic freedoms and police accountability.

Prime Minister Lee Hsien Loong said last month that Singapore would be "finished" if similar protests erupted there.

"It will become impossible to govern Singapore, to make and carry out difficult decisions or to plan for the long-term good of the nation," he said.