Christian human rights campaigner Benedict Rogers has condemned the Hong Kong police's increasing heavy handedness after a 12-year-old was reportedly among the dozens of protesters detained during a day of violent clashes on Sunday.

For the first time since the pro-democracy protests began in June, the police deployed water cannon and fired a live shot to clear the streets. 

The protests began in the district of Tsuen Wan before moving across to Tsim Sha Tsui, with 36 people arrested by the end of the day. 

Mr Rogers, East Asia Team for Christian Solidarity Worldwide, strongly criticised the police handling of the protests.

"When a 12 year old kid is arrested and a police officer shoots a gun you know a rubicon has been crossed," he said.

"Hong Kong is the new frontline in the battle for freedom against tyranny and repression and every freedom-loving person and government must stand with the Hong Kong people." 

He said that members of the Hong Kong government needed to "examine their consciences" in light of the escalating violence and asked that people pray for the city. 

The protests have been going on for the last 12 weeks, having been ignited by an extradition bill that would see some suspects sent to mainland China for trial.  They have since grown to reflect the fears of Hong Kongers more generally concerning democracy, human rights and police brutality in the former British colony. 

A key demand of the protesters is that Hong Kong Chief Executive Carrie Lam completely withdraws the bill, but there are others. They want Lam's resignation and a change in the official rhetoric branding the protests as "riots", as well as the unconditional release of arrested protesters.

An additional demand for an independent inquiry into the police response has been backed by Christian leaders. 

On Sunday, Lam posted a message in Facebook suggesting the creation of a "dialogue platform" between the Hong Kong government and protesters to find a way forward. 

"I do not expect dialogue to easily resolve the deadlock, stop demonstrations, or to provide solutions to problems," she said.

"But continuing to fight is not the way out."

She continued: "I know that in the current predicament, there is deep social resentment, and some citizens are very dissatisfied, or even angry with the government's failure to fully meet the 'five demands'. 

"There is growing resentment among people of different political views and citizens of different positions, and even hatred may grow."