HONG KONG -- Rioters on Saturday vandalized government buildings, set large fires on main streets, and paralyzed traffic, causing chaos in China's Hong Kong Special Administrative Region (HKSAR).

In the latest development, rioters traveled across Hong Kong's harbor to the Tsim Sha Tsui district, where they set fires and threw petrol bombs on Nathan Road. Witnesses said a rioter told people around that it was a "flash mob" action.

They also set up barricades with trash bins and debris, and paralyzed traffic in Mong Kok and Kwun Tong.

Earlier, rioters threw petrol bombs at government buildings and Legislative Council (LegCo), before they went on to set fires on a main street near the Hong Kong police headquarters.

Speaking through a spokesperson, President of the LegCo Andrew Leung said he felt extremely distressed and disappointed to see demonstrators storm the LegCo building once again, and sternly condemned the demonstrators for hurling inflammable objects and bricks in disregard of safety of the people present.

Leung urged the demonstrators to express their demands in a peaceful manner and called on all parties to work together to resolve social disputes and restore peace to Hong Kong soon.

Around 7:00 p.m., black-clad and helmet-wearing rioters gathered a large amount of barriers to block the Hennessy Road near the Hong Kong police headquarters in Wan Chai, poured inflammable liquids, and set the roadblock on fire. Huge black smoke billowed up the air.

As the fire grew drastically, explosions were heard. The fire lasted for about 30 minutes before being put out by the firefighters.

In a statement, the Hong Kong police said that radical protestors set multiple fires on roads in Wan Chai and Causeway Bay area, posing a serious threat to the safety of everyone, including police officers on site.

"The Police reiterate appropriate force will continue to be deployed to disperse the protestors. The Police warn protestors to leave immediately," said the statement.

The police warned the members of public in the area to keep their windows shut and stay indoors, if necessary.

Hong Kong police said Thursday they had banned the application of public processions on Saturday to ensure the safety of residents and public order after several similar events turned extremely violent recently.

However, protesters on Saturday defied the police ban by occupying downtown roads. During their marches, some radical protesters smashed traffic lights, and dismantled roadside railings to set up barricades to face off the police.

Around 5:00 p.m., the rioters, some of whom already had masks on and carried large backpacks, put on helmets and other protective wear.

They gathered around the headquarters of the HKSAR government and the Legislative Council and used sling shots to fire objects into the buildings.

Around 5:30 p.m., violent protesters repeatedly threw corrosive liquids and petrol bombs at the government and police headquarters, and the Legislative Council, said Yu Hoi-Kwan, senior superintendent of Police Public Relations Branch in a briefing.

"They also deliberately set fire to the water-filled barriers and posed grave danger to all of the people on site," she said.

Police raised flags to warn the rioters to stop charging, but the rioters responded by throwing petrol bombs at the police lines. The bombs caused fire to break out on the roads near the government headquarters.

The rioters also threw corrosives and bricks at officers.

After repeated and futile warnings, police deployed tear gas and colored water to disperse the rioters.

At one moment, protesters picked up tear gas grenades and threw them into the Hong Kong Garrison of the Chinese People's Liberation Army (PLA).

Also on Saturday, Hong Kong's railway operator, the MTR Corporation, condemned vandalism and other "irresponsible" acts by violent protesters.

According to the MTR Corporation, a screen door at Wan Chai station was vandalized and traffic cones as well as railings were hurled onto tracks.

As the riot dragged into the night, a number of MTR stations were vandalized by rioters. At Admiralty station, graffiti was sprayed which read: "You block (the stations), I spray (paint)."

Violent protesters have harrowed Hong Kong through confrontations with police and extensive vandalism since June. They have deliberately attacked police, besieged police stations, sabotaged public facilities and assaulted innocent people, forcing officers to respond to prevent further destruction.

On Friday night, an off-duty officer, 45, suffered heavy knife wounds in his arms and back after he was attacked by three males near Kwai Yi Road, said Hong Kong's Commissioner of Police Lo Wai-chung on Saturday.

When visiting the officer in the Princess Margaret Hospital, Lo expressed sadness and anger over the attack, saying such a brutal attack is contemptible. Wounding with intent is a very serious offence and is liable to life imprisonment, he said.

The Regional Crime Unit of New Territories South is investigating the attack.