Several hundred people demonstrated in front of the UK parliament, with some holding placards that read: "I oppose genocide. I support Palestine Action."

The capital's Metropolitan Police force (Met) had warned people that it would not hesitate to arrest anyone who explicitly expressed support for the prohibited group.

The Met said in a statement late on Saturday that it had arrested "more than 425 people... in relation to the protest".

"The majority of these arrests were made for supporting a proscribed organisation," the force said.

Polly Smith, a 74-year-old retiree, said those at the rally "are not terrorists", adding: "The ban must be lifted."

Nigel, a 62-year-old CEO of a recycling company who declined to give his surname, said the government's ban imposed in July was "totally inappropriate".

"They should spend more time working on trying to stop genocide, rather than trying to stop protesters," he told AFP before being arrested as protesters chanted "Shame on you!" at police.

Skirmishes broke out between officers and demonstrators who tried to prevent arrests.

More than 25 people were arrested for alleged "assaults on police officers and other public order offences", the Met said.

Deputy Assistant Commissioner Claire Smart said officers had been subjected to "intolerable" abuse, including being punched, kicked and spat on.

"Our role in the context of protest remains... to enforce the law, and to ensure those exercising their right to protest can do so safely," she said.

- Controversial ban -

Palestine Action was banned under the UK's Terrorism Act of 2000 following acts of vandalism including at a Royal Air Force base, which caused an estimated pound7 million ($10 million) in damage.

Critics, including the United Nations and campaign groups such as Amnesty International and Greenpeace, have condemned the ban as legal overreach and a threat to free speech.

More than 800 people had already been arrested before Saturday's demonstration, with 138 charged with supporting or encouraging support for a proscribed organization.

Most face six months in prison if convicted but organisers of the rallies could be sentenced to up to 14 years if found guilty.

The government has been granted permission to appeal an earlier ruling which allowed Palestine Action co-founder Huda Ammori to challenge the ban.

A separate pro-Palestinian demonstration saw around 20,000 people take to the streets elsewhere in London on Saturday, Smart said.

She added that those protests "passed with very few arrests".

The rallies came as Israel launched new strikes on Gaza, with the stated aim of seizing Gaza City to defeat the militant group Hamas.