Hong Kong police have been accused of re-writing history over their account of an attack on protesters in 2019, as two opposition lawmakers are arrested.
Last year, masked men suspected to be triad gangsters attacked pro-democracy protesters and passers-by in Yuen Long, injuring dozens and shocking the city.
However police now say the clashes were "between two evenly matched rivals" and deny that they were slow to respond.
One lawmaker who was hurt in the clash has now been held on "riot" charges.
A police source told the BBC that a total of 16 people, including the two lawmakers, had been arrested on Wednesday.
The legislators, Lam Cheuk-ting and Ted Hui Chi-fung from the Democratic Party, were arrested at their homes on Wednesday morning.
What happened in Yuen Long last year?
A violent attack on pro-democracy protesters and some passers-by on 21 July, at a train station in Yuen Long in north-west Hong Kong, was captured by victims and bystanders on mobile phones. Some of the protesters were returning home after a rally earlier that day.
The footage, which went viral on social media, showed groups of men dressed in white shirts and suspected to be triad gangsters beating passengers with rods.
Police were late to arrive on the scene and the incident contributed to growing mistrust of the force at a time Hong Kong was faced with widespread anti-government protests.
Police have so far arrested 44 people on suspicion of involvement in the Yuen Long mob attack, seven of whom have been charged with rioting, according to Reuters.
What are police saying now?
In a press conference, superintendent Chan Tin-chu said on Wednesday that live streams of the incident did not show the full picture.
The incident was not an "indiscriminate attack" but the result of clashes between two "evenly matched" rival groups, he said.
He also said that officers responded to the scene of the attack within 18 minutes - contradicting previous police reports that they took 39 minutes.
Mr Chan added that Mr Lam, who live streamed the attack and was hospitalised after being hit in the face, had been arrested on suspicion of rioting because his presence at the train station aggravated the incident.
Mr Lam and Mr Hui have also been arrested in connection with a protest on 6 July last year. Mr Lam is accused of conspiring to damage property and obstruction of justice, while officers said they were charging Mr Hui with attempted obstruction of justice, access to a computer with criminal or dishonest intent and criminal damage
What's the reaction been?
Activists and pro-democracy politicians have reacted with outrage to the arrests and the new police account of last year's attack.
A statement from some Yuen Long district councillors said: "They [police] altered history and erased facts so as to change public opinions, boost the force's morale and comfort themselves."
Meanwhile, a lawyer who has covered the protests, Anthony Dapiran said police were "trying to rewrite the narrative of one of the most documented and live-streamed events of last year", calling it "gaslighting of the highest order".
However, some pro-Beijing politicians have welcomed the arrests, with one, Junius Ho, saying this would take Hong Kong "back to the right path", and that "justice may be late but never absent".
On Wednesday, Twitter users reacted with outrage at Mr Lam's arrest.
"We know you were protecting citizens on the train on that day," wrote one. Another posted that the move kept "the actual instigators at large".
These latest arrests come two weeks after police arrested media tycoon and vocal Beijing critic Jimmy Lai under a controversial national security law that China recently imposed on Hong Kong.
Mr Lai was paraded through his Apple Daily newsroom in handcuffs as some 200 police raided the office as part of an operation that also saw nine other activists arrested, including Agnes Chow, a prominent youth activist.