It's a full on standoff between police and protesters in Hong Kong.

Police have formed a hard barricade from their plastic shields and are waving a banner saying "Warning, tear gas" in an attempt to keep protesters away, according to live coverage on local television outlets.

But protesters seem also undeterred, throwing traffic cones and other random objects they can get their hands on . The roads are already chock full with dented traffic cones and scattered umbrellas left behind by those who have already fled the scene.

Image source, AF

The Hong Kong Professional Teachers' Union has announced a strike against the controversial bill.

In a statement on Facebook, it described its decision to join the strike as a "tough" one, but said it needed to "protect the conscience of educators". It also urged teachers to explain to their students why they were protesting.

This map shows the parts of Admiralty and central Hong Kong where huge numbers of protesters have blocked main streets. It also shows the Legislative Council Complex which is a group of buildings that make up government headquarters. This is where violence has erupted.

This striking image shows a police officer lashing out at a protester using his baton.

Image source, Reuters

BBC cameraman Joe Phua has sent these images from outside the LegCo buildings saying it resembles a battleground.

Police have fired about a dozen tear gas rounds so far and baton charged protesters.

Protesters have fought back and pushed police back. They are angry, he reports.

One group has put a request on Twitter calling for anyone with asthma inhalers to make their way towards the downtown Admiralty station - where some protesters are presumably suffering from asthma attacks as a result of tear gas.

Police chief Stephen Lo Wai-Chung has called the clashes a riot.

This holds serious consequences - rioting is punishable by 10 years in prison, according to the South China Morning Post.The Post also adds that the 2014 Occupy Central movement had never been referred to as a riot."It's a riot now," said Mr Lo. "We had no choice but to use weapons to stop these rioters."

Protesters have forced their way into the Legislative Council (LegCo) building, the South China Morning Post reports. Police are trying to force them back with tear gas and smoke bombs, it adds.

Hong Kong's police chief has confirmed that officers used tear gas and rubber bullets against protesters, according to news wire Reuters.

What started out as a relatively peaceful protest several hours ago has now turned into a full blown scene of violence. Protesters can be seen fleeing the scene as police continue firing tear gas.

Image source, AFP

Image source, AFP

Image source, Reuters

Image source, Reuters

Images from the scene show protesters engulfed in clouds of tear gas. Police say they have been pelted with bricks and other debris.

It's chaos in Hong Kong as ambulances are now making their way towards the main site of the protests, according to news wire Reuters. Police had earlier fired tear gas and pepper spray to disperse protesters.

Martin Yip
BBC Chinese

It is predominantly young people occupying the protest site today. At the time of the Occupy Movement in 2014 in they would have been young teenagers or even children.

Now they have come of age and they are up for confrontation on the 'frontline'. It feels like a more militant atmosphere this time round and the protesters seem organised and determined - though they don't come from any coherent group and haven't been friends and fellow students the way Occupy protesters were.

One anomaly that stood out was an elderly lady, known as Auntie Wong, who kept waving the Union Jack in front of riot police until somebody physically removed her - albeit gently - before the violence broke out. Some protesters believe the more hardcore nature of the crowds out here now could be a byproduct of the failed Occupy Movement.

BBC Newsnight's Gabriel Gatehouse is inside the LegCo building where police have effectively barricaded themselves. He reports one officer is injured and was carried away. The doors have been padlocked.

Hong Kong police are continuing to fire shots of tear gas in an effort to disperse protesters, according to Reuters

Stephen McDonell
BBC News, Hong Kong

Protesters are racing up the hill towards the city from the harbour gasping for breath. The wind is blowing the tear gas in the same direction. Our eyes are all stinging as we try and file material with internet connections nearly impossible.

With every bang of tear gas fired more people run towards Harcourt Road. The more radical students are increasing their pressure on the police lines and the warnings from the authorities are also increasing as they call on tens of thousands of demonstrators to leave or they will increase the use of force.

Images allegedly taken from a local TV station are showing police officers armed with what are reportedly rubber bullet guns, according to this reporter from the South China Morning Post.

Image source, Reuters

Protesters are using their umbrellas as protection against pepper spray. Meanwhile, plumes of tear gas can be seen over the streets.

A video by WSJ reporter Mike Bird shows a scene of chaos as protesters run away from huge clouds of tear gas: