Two Australian reporters assaulted live on-air while covering London Black Lives Matter protests

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

Nine News' Europe correspondent Sophie Walsh was covering a Black Lives Matter protest in Hyde Park last night (NZT) when she was attacked.

In a separate incident, another Nine reporter, Ben Avery, was set upon in an underground tunnel while he was broadcasting live on the Today show this morning (NZT).

"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.

Earlier, Walsh was speaking during a live cross for Adelaide's 6pm news bulletin, but was not in front of the camera, when the incident happened as footage of the day's earlier protests in Paris was being screened.

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

In the footage 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 is heard saying to the presenter 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."

The man was chased down and detained 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 the Today Show.

"I did feel like that in a moment."

Walsh told AAP 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, which prompted an outpouring of support for the correspondent on social media.

"Thank you for your messages. The man has been arrested for threats to kill and carrying a weapon. I'm shaken but ok. Big thanks to my incredible cameraman Jason Conduit who chased him down armed with a light stand and got him arrested," Walsh wrote on Twitter.

Earlier this week, Seven news reporter Amelia Brace and cameraman Tim Myers were assaulted by police in Washington DC while covering a George Floyd protest.