Counter-terror police have arrested four people after two military planes were damaged at RAF Brize Norton.
A 29-year-old woman and two men, aged 36 and 24, were arrested on suspicion of the commission, preparation or instigation of acts of terrorism, Officers from Counter Terrorism Policing South East (CTPSE) said.
A 41-year-old woman was also arrested on suspicion of assisting an offender.
The arrests come after two Voyager aircraft were sprayed with paint during a break-in at RAF Brize Norton on June 20, in action claimed by campaign group Palestine Action.
The group previously posted footage online showing people inside the Oxfordshire base, with one person appearing to ride an electric scooter up to an Airbus Voyager air-to-air refuelling tanker, before spray painting into its jet engine.
CTPSE said the four arrests were made in London and the Newbury area of Berkshire on Thursday.
The force said in a statement: “CTPSE have arrested four people in connection with an investigation into an incident in which aircraft were damaged in Oxfordshire.
“A 29-year-old woman of no fixed abode, and two men; aged 36 and 24, both from London, were arrested on suspicion of the commission, preparation or instigation of acts of terrorism, contrary to Section 41 of the Terrorism Act 2000.
“A 41-year-old woman, of no fixed abode, was arrested on suspicion of assisting an offender.
“The arrests, which took place yesterday (26/6) in Newbury, Berkshire, and in London, are in connection with an incident in the early hours of Friday (20/6) during which damage was caused to two aircraft at RAF Brize Norton.
“Those arrested are currently in police custody while enquiries are ongoing.”
After the incident, the Home Secretary announced a decision to proscribe Palestine Action. This means support for the group will become a criminal offence punishable by up to 14 years in prison when the ban comes into effect as soon as next Friday.
The proposal has been heavily criticised by human rights groups such as Amnesty International and Liberty.
“The UK has an overly broad definition of terrorism and proscribing a direct-action protest group like Palestine Action risks an unlawful interference with the fundamental rights of freedom of expression, association and peaceful assembly,” a statement from Amnesty read.
“It should be remembered that proscribing Palestine Action not only makes membership of the organisation a criminal offence, through broadly worded speech offences such as ‘glorification’ it puts at risk the free speech rights of many other activists who are deeply concerned about the plight of Palestinians in the context of Israel’s ongoing genocide in Gaza.”