The Hong Kong Police has filed criminal charges against an 18-year-old Hong Kong student who was shot by a Police officer as pro-democracy protests hit a new level of violence.

Police told reporters that the student identified as Tsang Chi-kin was charged with two counts of assaulting a police officer and rioting as tens of thousands of black-clad protesters took to the streets of the semi autonomous territory on Tuesday.

The months-long pro-democracy protests which have engulfed Hong Kong began in June in reaction to a now withdrawn extradition bill.

The protests have since snowballed into calls for greater police accountability and an investigation into allegations of excessive use of force by security operatives in the country.

The shooting which took place on Tuesday last week marked the first time that a protester was struck by live ammunition.

Police officials however defended the officer, saying his life was in imminent danger and that he fired his gun as the teen struck him with a metal rod.

If found guilty, Tsang who has undergone surgery at Queen Elizabeth Hospital faces two years in prison for assaulting a police officer while the rioting charge has a prison sentence of up to 10 years.