Twelve people have been arrested on suspicion of making a right-wing terrorist threat to an Islamic event at a country estate in Suffolk, police said.
Counter Terrorism Police (CTP) in London said the UK Ijtima event at Shrubland Hall in Barham was stopped early on Sunday morning as a precaution following a possible threat.
Home Affairs Minister Shabana Mahmood said the police response to deal with the “credible threat” to the festival “undoubtedly saved lives”.
Commander Helen Flanagan, head of London’s counter-terrorism police force, said officers acted quickly to make arrests across the country.
CTP confirmed the investigation was “related to right-wing terrorism” and officers were carrying out searches at various addresses across the country linked to those arrested.
The report said eight people were arrested and detained under Section 41 of the Terrorism Act 2000 and remain in custody.
Three other men were arrested on suspicion of conspiracy to murder and a woman was arrested on suspicion of assisting an offender.
Of these, one person has since been released on bail, while three others remain in custody.
Police confirmed they declared a major incident as soon as they became aware of a “potential serious threat” to the event, but that designation has since been revoked.
Flanagan added that police “will not hesitate to act” if any potential threat arises.
“Unfortunately, this activity is a stark reminder that the threat level in the UK is ‘severe’, so we urge the public to remain vigilant and report anything if it looks or feels wrong.”
Mahmood added: “I know this news is deeply troubling for British Muslims.
“We must stand up to hate and must unite around our shared belief in a country that is open, generous and tolerant of all our communities.”
According to CTP, there is no expectation of any wider threat to society associated with this issue.