Thousands of people have gathered for pro-Palestinian demonstrations across the UK, amid international concern over the situation in Israel and Gaza.

A gathering in London attracted a crowd of thousands, with rallies also held in Manchester, Edinburgh and other parts of the UK.

More than 1,000 officers were deployed by the Metropolitan Police for Saturday’s demonstration in the capital, with police warning in advance that anyone showing support for militant group Hamas could face arrest.

It comes as Palestinians began a mass exodus from northern Gaza after Israel’s military told them to evacuate ahead of an expected ground invasion.

The UN, human rights groups and others have been among those expressing deep concern about the impact of Israeli action on civilians, as the death toll continues to grow amid airstrikes and a siege on the territory.

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Protesters during a Manchester Palestine Action demonstration and march in Manchester (Danny Lawson/PA)

The renewed violence came after an attack last week by the Palestinian militant group left hundreds of Israeli civilians and soldiers dead.

Protesters gathered outside the BBC’s Broadcasting House in Portland Place ahead of the London march on Saturday afternoon, waving Palestine flags and carrying placards.

Flares in the national colours of red, green and black were set off early on the route, while chants of “Free, free Palestine” could be heard as people made their way through the centre of the capital.

The Met said that certain areas of London would be covered by a Section 60AA power until 10pm, which requires a person to remove items such as masks that might be used to conceal their identity.

The London march started outside BBC Broadcasting House
The London march started outside BBC Broadcasting House (James Manning/PA)

Section 12 of the Public Order Act is also in force covering the demonstration route, which finishes in Whitehall.

Police warned that “action will be taken” against anyone in possession of, or found throwing, flares at the gathering.

As marchers arrived in the thoroughfare and made their way to a stage outside Downing Street, chants of “Rishi Sunak, shame on you” and “From the river to the sea, Palestine will be free” rang out among the crowd.

Home Secretary Suella Braverman earlier this week urged police chiefs to consider whether that pro-Palestine slogan could be amount to an offence, while also suggesting that waving Palestinian flags could in some contexts be seen as illegitimate.

Former Labour leader Jeremy Corbyn was among those addressing the crowd, as he urged political leaders to condemn Israeli actions in Gaza.

“As we wave the Palestinian flag, let’s hear it for the people of the West Bank, for the people of Gaza, for the people of the refugee camps, and say very bluntly to our political leaders in this country: ‘Do not condone war crimes, do not condone the starvation and the denial of medicine to desperate people in Gaza or anywhere else.’

“If you believe in international law, if you believe in human rights, then you must condemn what is happening now in Gaza by the Israeli army.”

A masked supporter shouts through a megaphone during the march
A masked supporter shouts through a megaphone during the march (Jeff Moore/PA)

Ahead of the demonstration the BBC’s headquarters in London was targeted and daubed in red paint as pro-Palestinian group of Palestine Action accused the broadcaster of having “blood on its hands”.

The BBC has also faced criticism in recent days from senior ministers for maintaining its editorial stance not to describe Hamas militants as terrorists.

The UK Government has been steadfast in support of Israel, with ministers also calling on police to use the “full force of the law” against shows of support for Hamas or bids to intimidate the UK’s Jewish community.

Amid concerns about the scale of the Israeli response, Prime Minister Rishi Sunak said on Friday that the country has “every right to defend itself” from Hamas attacks but stressed that civilian safety must be “paramount in our minds”.

Orly Goldschmidt, spokeswoman for the Israeli Embassy to the UK, earlier insisted that Israel was not targeting civilians, but admitted that innocent people would be casualties of the conflict with Hamas in Gaza.

“There will be innocent people who will pay tragically with their life, but this is a state of war and we have to prevent anyone from harming us again,” she told Times Radio.

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Thousands gathered in London on Saturday (James Manning/PA)

Overnight it emerged that an RAF flight had left Israel as part of a UK Government effort to get British nationals to safety.

A plane carried passengers to Cyprus, with the air force assisting the Foreign Office amid a limited availability of commercial flights.

Three Britons are confirmed to have died during last weekend’s assault on Israel, but reports have suggested at least 17 could be among the casualties.