Four police officers were injured after pro-Palestinian protesters in London set off fireworks towards officers and into crowds.
Scotland Yard said a dispersal order was authorised at 6.43pm on Saturday and would remain in place until 1am on Sunday.
More than 1,300 officers were on duty today as tens of thousands of people demonstrated in London.
A total of 29 people have been arrested after thousands of pro-Palestinian protesters gathered in London’s Trafalgar Square demanding a ceasefire in the Israel-Hamas war.
They were arrested for inciting racial hatred, other racially motivated crimes, violence and assaulting a police officer, the Metropolitan Police said.
Demonstrators climbed on top of the square’s famous fountains as the mostly peaceful group waved flags and banners on Saturday afternoon.
But police said some demonstrators had launched fireworks into crowds and toward officers.
There were scuffles with police as the evening went on, and smaller groups of protesters began moving away from the square.
At least one protester was seen carrying a banner which read “Let’s keep the world clean” with a picture of an Israeli flag being thrown into a bin.
Other protesters chanted “from the river to the sea, Palestine will be free”, despite controversy around the slogan’s meaning.
Home Secretary Suella Braverman has previously branded the slogan antisemitic and claimed that it is “widely understood” to call for the destruction of Israel.
However, pro-Palestinian protesters have contested this definition.
Effigies of dead babies were left on the ground in Trafalgar Square, next to pictures of children and candles.
The Met issued a dispersal order for an area around the square which will remain in force until 1am.
An order was also issued giving officers the power to require someone to remove any item being used to conceal their identity, the force said.
Commander Karen Findlay, who is responsible for policing in London this week, said: “The vast majority of people demonstrated peacefully during an extremely busy day in central London, with protests in a number of locations requiring a policing presence.
“It is disappointing that various splinter groups were again responsible for behaviour which has no place in London and we are determined to deal with this robustly. Fireworks were directed towards officers and four officers were injured.”