Protesters in Hong Kong took their cause Friday to one of the busiest airports in the world.

More than 1,000 demonstrators dressed in black filled the arrival hall at Hong Kong International Airport, where they greeted international visitors with chants of "There are no riots, there's only tyranny!"

Airport authorities said operations wouldn't be affected, but advised passengers to arrive early given the risk of disruption.

The former British colony, which returned to China in 1997, is embroiled in its worst political crisis for decades after two months of increasingly violent protests that have posed one of the gravest populist challenges to China's leader Xi Jinping since he took office.

Another march is planned for Saturday in Yuen Long, the neighborhood where a mob of white-clad men brutally attacked people at a rail station last Sunday following a large pro-democracy rally. Dozens were injured; police sources say some of the white-clad men had triad backgrounds.

Police refused to give permission for the Saturday event but protesters say they will move forward anyway.

The demonstrations, mushrooming up almost daily, saw the defacement of China's main representative office last weekend, triggering warnings from Beijing this was an attack on China's sovereignty.

What started as an angry response to a now-suspended extradition bill, which would have allowed defendants to be sent to the mainland for trial, now includes demands for greater democracy, the resignation of Hong Kong's chief executive, Carrie Lam, and even keeping mainland Chinese tourists out of Hong Kong.

Some protesters handed out flyers explaining the city's crisis to tourists. Others, dressed in helmets and seated on the ground of the arrivals hall, held up signs calling on the government to withdraw the extradition bill completely, while chants of "Free Hong Kong" reverberated around the building.

A demonstrator holds a sign warning tourists during a protest at Hong Kong's airport. (Edgar Su/Reuters)

"The world has been watching us in the past few weeks," said Jeremy Tam, a former pilot and lawmaker who helped organize the protest with other aviation sector employees.

"We simply believe that the airport is the most direct way for all tourists to explain what is happening in Hong Kong."

Singapore urged its citizens in a travel advisory on Friday to avoid parts of Hong Kong where protests may be taking place, noting the airport demonstration.

"If you are already in Hong Kong, you should take all necessary precautions to ensure your personal safety," it read.

"Protests which are meant to be peaceful may still have the potential to turn violent with little or no notice."