Animal Rebellion, a group which aims to “follow in Extinction Rebellion’s footsteps” and which wants to “end the animal agriculture industry”, has said it was behind the protest, in which demonstrators attempted to stop traffic entering the market.
Video footage showed dozens of demonstrators standing outside Billingsgate Fish Market in Poplar in the early hours of Saturday morning.
A Metropolitan Police spokesperson said 23 arrests had been made at the market, as of 9.30am on Saturday.
The spokesperson added that 22 of those arrests were for “knowingly failing to comply with a condition imposed under Section 14 of the Public Order Act 1986”, and one for aggravated trespass.
That figure could rise as more arrests are officially recorded, police said.
There have been more than 1,000 arrests in connection with Extinction Rebellion protests across London this week.
Alex Lockwood, an Animal Rebellion spokesperson, claimed 28 people had been arrested as of 7.45am and that one protester locked themselves to the entrance gate of the market.
A photo posted by the group showed a woman being carried away by three police officers, accompanied by the caption: “Mass arrests at Billingsgate”.
Mr Lockwood claimed about 200 people took part in the demonstration.
“One protester got inside [the market] and locked himself to the entrance gate,” he said. “It meant they had to shut down the site and police then moved in.”
He added: “We then sat down, which was obstructing traffic, and so they started arresting us.”
Mr Lockwood said the group stopped traffic from entering the market for about an hour between 5am and 6am.
In a tweet, Animal Rebellion described the protest as a “vigil”.
“So many here, here for the fishes, for the thousands in the market, dead or dying, for the trillions killed this year,” the group wrote.
It wants the government to lead a “transition to a just, sustainable plant-based food system”, according to the group’s website.
The group has said it stands in “solidarity” with the climate change campaigners Extinction Rebellion.
More than 100 healthcare professionals also joined the sixth day of climate change protests in London on Saturday.
Doctors, nurses and medical students took part in the "Health March for the Planet" near oil giant Shell's London HQ, in which some protesters carried Extinction Rebellion flags and signs reading: "Climate change is a health issue."
"We are meeting outside Shell because they are one of the biggest companies involved in the oil and energy industry, and they have real power to decarbonise that industry," Alex Turner, a paediatric and emergency doctor from Bristol, said.
"We are protesting illegal levels of air pollution."
Another protester said raising awareness of the health effects of climate change is part of their "duty of care as healthcare professionals".
Agencies contributed to this report
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