Tens of thousands of people have turned out in central London to protest the bombing of Gaza which has so far killed close to 2,000 people.
The demo, organised by the Palestinian Solidarity Campaign and Stop the War (STW), marched from the BBC's Broadcasting House via Regent Street, Oxford Street, the American Embassy in Grosvenor Square and on to Hyde Park for an afternoon rally.
Saturday's rally came as the Disasters Emergency Committee said its appeal for donations to help people affected by the conflict in Gaza has raised more than #4.5 million in under 24 hours.
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The demonstration's hashtag #gazA9 trended on Twitter throughout the afternoon.
Many waved placards and the Palestinian flag, chanting "Free, Free Palestine!"
Yasmin Rackal, 17, said: "People shouldn't stand by and watch an injustice. I have little brothers and sisters and if I was in that situation I would want people globally to fight for me."
Sanum Ghafoor, 22, had travelled from Luton to take part. She said: "It is a massacre of the Palestinians, and the world is staying quiet. The British Government keeps supporting the Israeli establishment.
"We want them to impose an arms embargo and put pressure on the Americans to stop supporting the Israeli government."
Philip McCowen, 59, a driver from Bristol, said: "The massacre of children is outrageous. The bombing of hospitals is outrageous. Collective punishment is a crime against humanity."
It is the second and larger major demonstration in London about Gaza since the current conflict began.
On July 19, shortly after Israel began a ground offensive in the territory, around 15,000 people marched through the city.
A 72-hour ceasefire held earlier this week after more than 1,900 Palestinians - three quarters of them civilians - were killed and 67 Israelis died, 64 of them soldiers. But hostilities have now resumed and casualties are mounting again.
Israeli reportedly struck more than 20 targets Saturday and killed a senior Hamas member.
The Israel Defence Forces said Hamas fired five rockets from Gaza on Saturday toward Israel, bringing the number fired since the truce expired on Friday to.
The IDF has targeted more than 30 sites in Gaza in the same period, it said.
There are concerns that members of the Jewish community who had joined the march felt intimidated while others had stayed at home because they were too afraid to attend today's protest.
Dan Rosenberg, 43, a Jewish stay-at-home father-of-two, said he is appalled at the "horrific" images of dead bodies and bombed-out homes being beamed out of Gaza.
But he said that while many of his Jewish friends felt the same, the "hatred" and extreme attitudes which has coloured much of the discussion about the conflict had left them too afraid to join the throng of protesters.
Mr Rosenberg, from Finchley in north London, said: "It is horrific what is going on in Gaza. It is collective punishment. I don't know how any human being can stand back while this is happening.
"But it is difficult being here. We have seen the anti-Semitic attitudes and you feel very threatened and scared, but we feel we have to stand up and represent.
"Even standing here we feel quite uncomfortable. You hear people say they think the Jews run the media. Those beliefs are unpleasant, ignorant and racist.
"I have Jewish friends who wanted to come but they felt uncomfortable being here."
The demonstration route takes in the Broadcasting House as a protest against what the demonstration's organisers see as the BBC's "biased" reporting of Gaza.
STW has accused the corporation of pro-Israeli coverage of the war and last month organised a 5,000 strong protested outside Broadcasting House.
The Metropolitan Police declined to give any estimates for the size of the crowd at today's protest but said it had "an appropriate and proportional policing plan" in place that includes numerous road closures.