Hong Kong police have come under fire after footage of officers tackling a 12-year-old girl to the ground near a pro-democracy protest went viral.

Police say the girl took part in an illegal gathering and officers used "minimum force" after she "ran away in a suspicious manner".

The girl's family say she was simply out to buy school supplies and became scared when confronted by police.

Nearly 300 people were arrested at Sunday's unauthorised demonstration.

The protests were over the government's decision to postpone elections to Hong Kong's parliament by a year. The government said this was necessary amid the coronavirus pandemic, but activists said the government was using the outbreak as a pretext to stop people from voting.

What does the video show?

The video, from Sunday afternoon, shows two police officers approaching a young girl in the Mong Kok area and telling her to stand still.

The girl starts running - and one officer taps her with his baton while another runs towards her and tackles her to the ground.

More riot police emerge, holding the girl and her brother, who had tried to help her, on the ground. Other officers tell journalists and bystanders - many of whom appear outraged at the police action - to stand back.

Local media say the girl and her older brother were later treated in hospital for light injuries. Police issued them and a passer-by with penalty tickets for violating social distancing rules that prohibit gatherings of more than two people.

What is the girl's version of events?

The girl, whom local media are only identifying as "Pamela" to protect her identity, said she lived nearby and was out to buy art supplies for school.

"The streets were cut off by police cordons so we had to double back to meet our family... but the police suddenly ran towards us. I was scared. They told us to stand still, but I panicked so I ran," she told i-Cable news.

Her brother added that they both intended to contest the fine they had been given for breaching social distancing rules.

"We were just walking by, so there was no reason for the police to come after us," he said.

Their mother said she had been out buying groceries with them but went home while they went to look for art supplies. She said she was angry at how they had been treated by police.

What do Hong Kong police say?

In a statement, police said they had been intercepting protesters in Mong Kok who had refused to disperse following warnings to leave.

Police said officers had wanted to "stop and search" the girl, but "she suddenly ran away in a suspicious manner. Officers therefore chased and subdued her with use of minimum necessary force".

Following an investigation, they determined that "she and other protesters at the scene were participating in a prohibited group gathering" and breaching coronavirus regulations, so they were given penalty tickets.

The police added that they were "concerned about youngsters participating in prohibited group" gatherings that could endanger "their own personal safety", and that they hoped young people would "stay away from high-risk protests and avoid putting themselves in danger".

Why are things so tense between protesters and the police?

Hong Kong saw months of anti-government protests in 2019. The demonstrations were initially about a proposed law that would have allowed extraditions to mainland China - however, the government's response was criticised and police were accused of responding to protests in a heavy-handed manner.

The protests, which involved a large number of young activists, soon evolved into a wider pro-democracy movement that also demanded an investigation into alleged police brutality.

Several high-profile incidents, including an alleged triad attack on protesters that police were slow to respond to, and violent clashes between protesters and police, led to relations deteriorating further.

Thousands of people, including students and children aged between 12 and 15, have been arrested in connection with anti-government protests.

One opinion poll suggests that Hong Kongers' approval of the police dropped from 66.9% in 2017 to 36.8% in 2020.