British counterterrorism police have arrested four people in connection with a pro-Palestinian, anti-Israel protest last week in which military planes were sprayed with paint at an air base in England, authorities said on Friday.

A woman, 29, and two men aged 36 and 24, were arrested on suspicion of the commission, preparation or instigation of acts of terrorism, while another woman, 41, was arrested on suspicion of assisting an offender, the police statement said.

Two activists from the Palestine Action group broke into the air base in Oxfordshire in central England on June 20, spraying red paint over two planes used for refuelling and transport, and further damaging them with crowbars, an act that was condemned by UK Prime Minister Keir Starmer as “disgraceful.”

Within days of the incident, UK Interior Minister Yvette Cooper set out plans to use anti-terrorism laws to ban Palestine Action, saying its actions had become more aggressive and caused millions of pounds of damage.

Palestine Action has regularly targeted British sites connected to Israeli defense firm Elbit Systems and other companies in Britain linked to Israel since the start of the conflict in Gaza.

In response to Friday’s arrests, the campaign group accused authorities of “cracking down on non-violent protests which disrupt the flow of arms to Israel during its genocide in Palestine.”

The maximum sentence for the preparation of terrorist acts, or to assist others in such preparation, in Britain is a life sentence. The UK government is also reviewing security across all defense sites.

Israel has repeatedly dismissed accusations that it is committing genocide in the war in Gaza, which began when Hamas invaded Israel on October 7, 2023, killing some 1,200 people and taking 251 hostages.

The IDF’s retaliatory offensive in Gaza has killed more than 56,000 Palestinians, according to the Strip’s Hamas-led health ministry. The toll cannot be verified and does not differentiate between civilians and fighters.

Israel says it has killed some 20,000 combatants in battle as of January and another 1,600 terrorists inside Israel during the October 7 onslaught. Israel also says it seeks to minimize civilian fatalities and stresses that Hamas uses Gaza’s civilians as human shields, fighting from civilian areas including homes, hospitals, schools, and mosques.