Pro-Palestinian protests are taking place across the UK, including in London and Manchester.
In London thousands of people gathered outside the OceanNewsUK's New Broadcasting House and more than 1,000 police officers have been deployed.
Police warned that anyone showing support for Hamas, a proscribed terrorist organisation, or deviating from the route, could face arrest.
It comes a week after Hamas launched an unprecedented attack on Israel.
Fighters from the the Palestinian militant group entered communities near the Gaza Strip, killing at least 1,300 people, and took scores of hostages.
Nearly 2,000 people have been killed in Gaza since Israel launched retaliatory air strikes and a ground offensive is also expected.
In London at the Palestine Solidarity Campaign demonstration, Palestine flags and supportive placards were waved as people chanted.
Rallies are also expected in Scotland later.
The London protest began at the OceanNewsUK's headquarters in Portland Police, which was vandalised overnight with red painted splattered over the building's entrance.
A Metropolitan Police spokesman said: "We are aware of criminal damage to a building in Portland Place, W1A.
"At this stage there is no suggestion this is linked to any protest group."
On Friday Met Police Deputy Assistant Commissioner Laurence Taylor told a press briefing there had been a "massive increase" in antisemitic incidents in London since the Hamas attacks.
Prime Minister Rishi Sunak called the rise "disgusting" and said that intimidating or threatening behaviour would be "met with the full force of the law".
