LONDON — More than 20 people were arrested in London yesterday for allegedly supporting the newly banned group Palestine Action, just hours after its proscription as a terrorist organisation took effect.

The UK government outlawed Palestine Action last month under anti-terror laws, following its activists’ break-in at an RAF base to protest Britain’s support for Israel. An urgent appeal against the ban was rejected late Friday, making it illegal from midnight to support the group, display its symbols, or express approval — offences punishable by up to 14 years in jail.

Supporters gathered in Parliament Square with placards reading “I OPPOSE GENOCIDE. I SUPPORT PALESTINE ACTION,” with several arrested near a Gandhi statue while chanting slogans.

Palestine Action has long targeted Israel-linked firms in Britain, which the UK home minister called criminal and violent. Critics, including UN experts and rights groups, argue the ban wrongly equates property damage with terrorism.

Separately, five Youth Demand activists were arrested after throwing red paint on a Cisco truck at London’s Pride parade, accusing the company of aiding Israel. Police cleared the protest and the parade resumed.