Hong Kong authorities have arrested 19 people, after violent fighting between pro-democracy protestors and local residents continued overnight.

Local media reports that at least 18 people, including police officers, were injured in the overnight clashes.

Yesterday approximately 1,000 people surrounded and attacked 200 pro-democracy protestors in Mong Kok – a busy shopping area – and Causeway Bay areas of Hong Kong.

The attackers tore down barricades and tents set up by activists, and also attacked people involved in the protests.

Initial reports said the cause of the attacks was frustration at the disruption caused by the protestors. But it is unclear where the protestors were from.

Rumours have identified the attackers as business owners from the Northern Territories, members of Triads (Chinese organised crime organisations), and members of the Chinese military acting as agent provocateurs.

Many of the attackers denied being linked to Triads or China, expressing they were simply annoyed at the disruptions caused by the protest.

Local media reported that anti-Occupy protesters chanted "This is not democracy, we need to feed our kids!" and "Beat them to death, good job police!"

Pon Sze-hang, 21-year student participating in a sit-in at Mong Kok, said he was not afraid of the threats made by residents against the protest camps.

He told the South China Morning Post: "No, as long as the crowds are big... if there are triad people, we can just run to the next street. Mong Kok is very important, extending the battle front is important, so there is no reason to retreat."

Soon afterwards, more pro-democracy protestors arrived, and surrounded the anti-democracy invaders.

Hong Kong police described the situation as "chaotic" and the city's chief executive, Leung Chun-ying, said it was "close to anarchy". Chun-ying has refused to resign over the protests, but offered to hold talks over the city leader elections.

Police accused of ignoring attacks

Witnesses said that police attempted to keep the two sides separate, but there were insufficient officers on the scene.

Leaders of the pro-democracy protests accused Hong Kong police of deliberately failing to protect demonstrators. The police have denied the accusations, saying they arrested 19 people, including members of triad organisations.

Fellow activists stop an anti-Occupy protestor from being sexually assaulted, before police intervene.

The accusations have led to the Hong Kong Federation of Students suspending preparatory talks with Hong Kong authorities.

"The government allowed the mafia to attack peaceful Occupy participants. It has cut off the path to a dialogue, and should be responsible for the consequences," it said, according to a BBC report.

Benny Tai, leader of Occupy Central, told the BBC the group was considering boycotting the talks, and that the police's failure to defend pro-democracy protestors could not continue.

The timing and location of the proffered talks had yet to be confirmed.

John Tsang, Hong Kong's finance secretary, has warned that the protests could harm the city's status as a premiere trading hub.

"If this situation were to persist, we're going to see some damage to our system," Tsangtold a press conference, warning a reduction in the "confidence in the market system in Hong Kong" would lead to "permanent damage".

The clashes began after people returned to work in Mong Kok and Causeway Bay, after a two-day holiday.

Hong Kong residents have tweeted that businesses are open as normal in the Mong Kok area, despite protests continuing.

The protests began when Beijing's central government announced that it must approve all candidates for the upcoming chief executive election.