Organisers claimed as many as 100,000 people braved the cold December conditions to join the demonstration - the first such protest since a week-long pause in the fighting broke down last week.

However, the Metropolitan Police said an estimated 40,000 people attended the march and 13 people have been arrested.

Protesters carried signs bearing the words "free Palestine" and "end the siege".

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Some protesters chanted: "One, two, three, four, occupation no more, five, six, seven, eight, Israel is a terrorist state."

They also chanted the controversial slogan: "From the river to the sea, Palestine will be free."

The Met Police said the 13 arrests were made mostly for offensive placards, as well as for other alleged offences including possession of drugs and obstruction.

It said a man was arrested on suspicion of a racially aggravated public order offence after "officers identified a man with a placard making comparisons between Israel and Nazi Germany".

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Sky News correspondent Emma Birchley, reporting from the march, said there was added frustration that a UN resolution calling for an immediate ceasefire had been vetoed by the US, with the UK abstaining.

Each time the crowd was reminded of that abstention from the stage beside the Houses of Parliament, they booed.