Riot police used batons and pepper spray early today to disperse crowds after clashes erupted when authorities tried to move illegal street vendors from a working-class district, the worst street violence since pro-democracy protests in late 2014.

Protesters hurled bricks at police as scuffles broke out, while other demonstrators set fire to rubbish bins in the streets of Mong Kok, a gritty neighbourhood just across the harbour from the heart of the Asian financial centre.

Police fired two shots into the air, a police spokeswoman said, amid chaotic scenes. Rubbish bins, chunks of brick and broken bottles lay scattered along the world-famous Nathan Road shopping strip today morning.

About 40 police vans were parked nearby.

The clashes broke out after police moved in to clear "hawkers", or illegal vendors who sell local delicacies, trinkets and household goods from makeshift streetside stalls.

The hawkers, long a common sight on Hong Kong's bustling streets, quickly attracted a strong social media following under the hashtag #FishballRevolution.

"To ensure public safety and public order, police took resolute actions, including using baton and pepper spray, to stop the unlawful violent acts," police said in a statement.

The protesters later dispersed . More than 100 confronted police in a tense stand-off hours before on the Chinese New Year holiday, when most of the city is shut down, with rubbish bins and flower pots in flames nearby.

The narrow streets in and around Mong Kok were the scene of some of the most violent clashes during protests in late 2014 to demand greater democracy in the former British colony that returned to Beijing rule in 1997.

- Reuters