Hong Kong protesters plan to hold a rally on Thursday in support of pro-independence demonstrators in Catalonia.
The protests in Catalonia bear some resemblances to the demonstrations in Hong Kong where millions have taken to the streets to express their anger on what they see as Beijing's tightening grip on the city.
Chinese forces have denounced the situation in Hong Kong as "mad violence".
"It has become more and more clear that it is not a peaceful demonstration in Hong Kong at all, but a violent crime that is mad," Xie Feng, the Commissioner for the Chinese Foreign Ministry in Hong Kong, said in a speech on Thursday.
"...The real purpose of the Hong Kong opposition and the foreign forces behind it is to disrupt Hong Kong, overthrow the legitimate government, and seize the power of governance. It is to turn Hong Kong into an independent or semi-independent political entity and subvert 'one country, two systems'. This is a delusion. Hong Kong is China's Hong Kong."
A poster advertising Thursday's demonstration of solidarity with protesters in Catalonia said: "United We Stand Against Tyranny".
Demonstrators in Catalonia, who protested for nine consecutive nights from October 14, are angry over the conviction of their leaders for sedition and at what they see as attempts to thwart their ambition for greater autonomy from the rest of Spain.
Some Hong Kong protesters went online to urge people not to attend the show of support for the Catalan movement, saying it was too provocative and risked denting international support for their own cause.
Hong Kong authorities formally banned a group promoting independence from China in September last year, the first time a political organisation has been outlawed since the 1997 handover.