The PKK is banned as a terrorist organisation in Turkey, the US and UK, and has been fighting against the Turkish state since the 1980s for greater rights for the country’s significant Kurdish minority.

Officers are carrying out searches at at least eight addresses across the capital, including the Kurdish Community Centre in Haringey, as part of the investigation.

The search is expected to last up to a fortnight, with the centre and surrounding area closed to the public in the meantime.

Following the arrests large crowds gathered outside the community centre and remained there into the evening. Videos show dozens of police forming a line and pushing protesters back.

Scotland Yard confirmed four protesters were arrested on suspicion of support for a proscribed organisation, assaulting an emergency worker, making threats to kill and a racially aggravated public order offence.

Ishak Milani, of the Kurdish People’s Assembly in the UK, described the raids on “community spaces” as “unjust and heavy-handed”.

“This aggressive act is not only an attack on our people but also an affront to the principles of democracy, justice, and human rights that the UK claims to uphold,” he said.