Australian journalists have been assaulted in separate incidents while covering protests in London.

Demonstrators clashed with police as thousands flooded into central London to protest the killing of George Floyd in police custody in Minneapolis.

Nine News’ Europe correspondent Sophie Walsh was covering a Black Lives Matter protest in Hyde Park on Wednesday morning (local time) when she was attacked.

In a separate incident, another Nine reporter, Ben Avery, was set upon in a tunnel while he was broadcasting live on the Today show on Thursday (Australian time).

“As you just saw there, the microphone was snatched out of Ben’s hands. I’m pleased to say that Ben is OK,” newsreader Alex Cullen said.

Activists chanted “black lives matter” and “we will not be silent” during a peaceful protest in Hyde Park before tensions escalated near the British Prime Minister’s Downing Street office.

Footage showed objects, including signs and a traffic cone, being thrown at police. One protester was wrestled to the ground and restrained by officers.

Walsh was doing a live cross for Adelaide’s 6pm news bulletin, but was not in front of the camera, when she was grabbed as footage of the day’s earlier protests in Paris was being screened.

Police officers and protesters at a Black Lives Matter protest in London. Photo: AAP

A man allegedly yelled “Allah Akbar” before making stabbing motions and grabbing Walsh.

Walsh can be heard to scream before camera operator Jason Conduit armed himself with a light stand and chased the man into the park.

“S—, sorry, sorry,” a shaken Walsh says as she watches the men run away.

“Yeah, a man just came up and grabbed me, but he’s OK, he’s not armed. A man just came up and grabbed me though.”

Tweet from @sophie_walsh9

The man was chased and held by Conduit and passers-by until police arrived and arrested him.

Officers found the man had a screwdriver and charged him with threats to kill and possessing an offensive weapon.

“I don’t think anyone knows the sound of their true scream until they’re in a situation like that, where they feel like it’s a life-or-death scenario,” Walsh told Today on Thursday.

“I did feel like that in a moment.”

Walsh said a nearby photographer had said the man also claimed to have put a bomb in a bin.

She said she was rattled but not physically harmed by the unprovoked attack.

Tim Myers and Amelia Brace flee police in Washington on Monday.

The attacks in London came only days after a Seven Network crew was assaulted by police on the sidelines of a demonstration near the White House in Washington.

Two US officers have been placed on administrative leave after journalist Amelia Brace was struck by a truncheon and Tim Myers punched and hit with a shield. They had been hiding behind a fence when US Park Police in riot gear aggressively cleared Washington DC’s Lafayette Square of protesters on Monday, ahead of a visit to a church by US President Donald Trump.

“As is consistent with our established practices and procedures, two US Park Police officers have been assigned to administrative duties, while an investigation takes place regarding the incident with the Australian Press,” Park Police acting Chief Gregory Monahan said on Wednesday.

Brace and Myers, who were doing a live cross back to Australia when they were struck, said they were also shot with rubber bullets and struggled to breathe after tear gas was fired into the crowd.

Seven news and public affairs director Craig McPherson described the police actions against Brace and Myers as “nothing short of wanton thuggery”. Australian Foreign Affairs Minister Payne has asked the Australian embassy to investigate.

-with AAP