Hong Kong Police fired tear gas Thursday on masked pro-democracy protesters and Halloween revelers in the territory's nightlife district.

Riot police began firing tear gas shells after the demonstrators urged others to celebrate Halloween wearing masks, including those depicting Carrie Lam, the city's embattled chief executive, Chinese President Xi Jinping or other government officials.

Protest organizers appealed to supporters to wear face coverings to test the city's recent emergency law banning masks at public gatherings.

Police slowly pushed back people from the Lan Kwai Fong district but it was not immediately clear if clashes had occurred or if there were arrests.

Police also fired tear gas to disperse hundreds of protesters, many wearing masks, on one of the major thoroughfares in Kowloon, an area in northern Hong Kong on the other side of Victoria Harbor.

Hong Kong police say they would deploy extra officers to the Lan Kwai Fong district and would demand anyone suspected of being a protester to remove their masks or facepaint. But Halloween masks are not covered under the ban, which will make it difficult for police to tell the difference between a protester and an ordinary reveler.