LONDON – Police in London have arrested at least 150 people for intentionally violating a new law banning support for a pro-Palestinian group.

Backers of Palestine Action have staged a series of protests across the U.K. since early July, when Parliament outlawed the group and prohibited anyone from publicly showing support for it. Lawmakers banned the group as a terrorist organization after activists broke into a Royal Air Force base and vandalized two tanker aircraft.

Protesters, who say the legislation improperly restricts freedom of expression, gathered Saturday afternoon in the square outside Parliament, with dozens displaying signs reading “I oppose genocide. I support Palestine Action.” That was enough for police to step in.

“While many of those remaining in the Square are media and onlookers, there are still people holding placards supporting Palestine Action,” the Metropolitan Police Service said on X. ”Officers are steadily working through the crowd making further arrests.”

Home Secretary Yvette Cooper moved to ban Palestine Action after activists broke into a British air force base in southern England on June 20 to protest British military support for Israel’s war with Hamas. The activists sprayed red paint into the engines of two tanker planes at the RAF Brize Norton base in Oxfordshire and caused further damage with crowbars.

Palestine Action had previously targeted Israeli defense contractors and other sites in Britain that they believe have links with the Israeli military.

Supporters of the group are challenging the ban in court, saying the government has gone too far in declaring Palestine Action a terrorist organization.

“Once the meaning of ‘terrorism’ is separated from campaigns of violence against a civilian population, and extended to include those causing economic damage or embarrassment to the rich, the powerful and the criminal, then the right to freedom of expression has no meaning and democracy is dead,” the group Defend Our Juries said on its website.

The arrests outside Parliament came amid what is expected to be a busy weekend of demonstrations in London as the war in Gaza and concerns about immigration spur protests and counter-protests across the United Kingdom.

While Prime Minister Keir Starmer has angered Israel with plans to recognize a Palestinian state later this year, many Palestinian supporters in Britain criticize the government for not doing enough to end the war in Gaza.

Pro-Palestinian protesters were gathering Saturday afternoon in central London for a march that is scheduled to end outside the gates of No. 10 Downing Street, the prime minister’s official residence and offices.

On Sunday, a number of groups are scheduled to march through central London to demand the safe release of the Israeli hostages in Gaza. Palestinian militants have held the captives since they attacked Israel on Oct. 7, 2023.

Police are also preparing for protests outside hotels across the country that are being used to house asylum seekers. Protesters and counter-protesters have squared off outside the hotels in recent weeks, with some saying the migrants pose a risk to their communities and others decrying anti-immigrant racism.

Deputy Assistant Commissioner Ade Adelekan said the scale of the events would “put pressure” on the police department.

“This is going to be a particularly busy few days in London with many simultaneous protests and events that will require a significant policing presence,” Adelekan said before the protests began.