A Hong Kong court on Monday threw out two private prosecutions -- including one against a police officer who shot a pro-democracy protester last year -- following a rare intervention from the financial hub's justice secretary.

Ted Hui, an opposition lawmaker, brought the private cases after prosecutors declined to press charges over two incidents during last year's huge and often violent anti-government protests.

The first was a dangerous driving case against a taxi driver who ploughed his car into a crowd of demonstrators in early October, injuring two women. The other focused on a police officer who shot a masked protester in the chest a month later, with Hui attempting to bring a grievous bodily harm prosecution.

But on Monday a magistrate threw out both cases days after Justice Secretary Theresa Cheng announced she was using her powers to end the prosecutions. Spectators in the public gallery heckled prosecutors on their way out of court on Monday, an AFP reporter on the scene said, as the two cases were formally shelved.

Tensions are running high within the city's legal system, which is prosecuting hundreds of cases against protesters arrested during last year's demonstrations. In June, Cheng warned on her official blog that she would end any private prosecutions "which are groundless or frivolous or brought out of improper motives or political considerations".

But activists have accused officials of cutting off a way for citizens to seek redress. "I am disappointed by today's ruling and I am extremely furious about the Department of Justice's intervention and termination of the cases," Hui told reporters outside court. 

"I will continue to lodge private prosecutions and I hope Hong Kong people can continue to exercise this right provided in the common law system to seek justice," he added.

The taxi driver who drove into crowds of protesters was beaten bloody soon after the incident and previously told local media he did not know how his car veered out of control.  Two people allegedly involved in his beating were arrested for rioting.

The 21-year-old who was shot a month later by police survived his wounds and has been charged with obstructing police, attempting to escape custody and attempted robbery of the officer's gun.

No disciplinary proceedings have been launched against police for actions taken during last year's protests, including three officers who shot demonstrators with live rounds. The police have argued that their levels of force were justifiable throughout.