A total of 27 police officers were hurt during anti-racism protests in London, the Met Police has revealed.
Dame Cressida Dick, Met Police Commissioner, said the attacks were "shocking and completely unacceptable".
Protests on Saturday - sparked by the death of George Floyd - were largely peaceful, but were marred later by disturbances outside Downing Street.
One demonstrator, who was not at Downing Street, saw officers "acting very aggressively" elsewhere.
Further demonstrations are taking place across the UK including in Bristol, where the statue of a prominent slave trader has been pulled down.
In a statement Dame Cressida, the UK's most senior officer, thanked officers at Saturday's protests in London for their "extreme patience and professionalism".
"I am deeply saddened and depressed that a minority of protesters became violent towards officers in central London yesterday evening," she said.
"This led to 14 officers being injured, in addition to 13 hurt in earlier protests this week.
"We have made a number of arrests and justice will follow. I know many who were seeking to make their voices heard will be as appalled as I am by those scenes.
"I would urge protesters to please find another way to make your views heard which does not involve coming out on the streets of London, risking yourself, your families and officers as we continue to face [the deadly coronavirus]."
The majority of Saturday's protests were peaceful but in the evening there were disturbances outside Downing Street.
BBC home affairs correspondent Tom Symonds said the protest was largely over when missiles and fireworks were thrown at a police line.
Two officers were seriously injured, including a Mounted Branch officer who was knocked from her horse when it hit a set of traffic lights whilst appearing to bolt.
She suffered a broken collarbone, a broken rib, and punctured lung, according to the Metropolitan Police Federation
The officer had struggled to stay in control as she was riding down the street surrounded by protesters.
She remains in hospital in a stable condition after undergoing surgery.
But Asia Ahmed, an activist who attended several of the protests, said "these situations don't come from nowhere".
She told the BBC she had seen the police "acting very aggressively" towards protesters.
Ms Ahmed, who was not at Downing Street during the disturbance, said a "lot of people" she spoke to "feared for their lives when they saw police horses".
"I don't think that was the best tactic to use if you're trying to create a peaceful environment," she said.
Police arrested 29 protesters for variety of offences, including violent disorder, public order offences and assault on emergency service workers.
The Mayor of London, Sadiq Khan, said the pockets of violence were "simply not acceptable".
He said: "I stand with you and share your anger and pain. George Floyd's brutal killing must lead to immediate and lasting change in countries, cities, police services and institutions everywhere.
"But this vital cause was badly let down by a tiny minority who turned violent and threw glass bottles and lit flares, endangering other protestors and injuring police officers."
A rally is currently being staged outside the US Embassy in Battersea, south-west London.