A security guard sweeps up shattered glass inside Xinhua office, after it was damaged by protesters

Cleaners swept up broken glass at the Hong Kong office of China's official news agency Xinhua on Sunday, one of the buildings vandalised in a violent day of protests which also saw activists hurl petrol bombs and set fire to metro stations.

More than 200 people were arrested in one of the worst outbreaks of violence in recent weeks as around five months of protests show no signs of abating. Demonstrators are angry at perceived Chinese meddling with Hong Kong's freedoms since the city returned from British to Chinese rule in 1997, a charge which China denies.

While protesters have previously vandalised buildings of mainland Chinese firms or those perceived as pro-Beijing, the targeting of Xinhua is one of the most direct challenges to Beijing yet. Protesters daubed China's Liaison Office, the key symbol of Chinese sovereignty, with graffiti in July.

Xinhua condemned the attack by what it said were "barbaric thugs" who broke doors and security systems and threw fire and paint bombs into the lobby.

"The practice of the black rioters once again shows that 'stopping the violence and restoring order' is Hong Kong's most important and urgent task at present," a spokesperson for Xinhua said in a Facebook post.

Xinhua condemned the attack on its office by protesters who "broke doors and security systems and threw fire into the lobby"

When Reuters visited on Sunday, a handful of cleaners could be seen through shattered glass doors and windows sweeping the floor, watched over by staff members speaking on their phones. Outside, some tourists and other media curiously eyed the destruction.

There are no major demonstrations planned for Sunday, although some groups had called for a protest walk in several districts of the city starting in the afternoon.

Cat-and-mouse clashes between riot police and demonstrators continued into the early hours of Sunday morning after police broke up an assembly of thousands on Saturday afternoon by firing tear gas into a park.

Hong Kong police said they had arrested more than 200 people overnight for offences including unlawful assembly, possession of offensive weapons, criminal damage, and wearing masks which is now illegal under a revived colonial-era emergency law.

Police fired tear gas, rubber bullets and deployed a water cannon at protesters during Saturday and early Sunday, they said, as the violence spilled from Hong Kong island across the water to the northern Kowloon side.

While the protests have broad support, the destruction and impact on transport networks has irritated some local workers.

"It's good that they are doing the protest but (there are) also the bad things," said 30-year old Bikash, a Hong Kong resident originally from Nepal who works in a bar district targeted by masked Halloween protesters earlier this week.

"The worst was I need to go to work (and)...everything was closed. That was very bad because our bosses they don't understand."