Hactivist group Anonymous claims to have taken down the websites of Interpol and a British police force as part of a campaign calling for the freedom of WikiLeaks founder Julian Assange.

Several Twitter accounts associated with the loose-knit Anonymous collective have announced that the website of International Criminal Police Organization was taken down. The site was unavailable as of 9:18 pm GMT on Sunday but resumed functioning soon after.

The hackers also claim to have taken down the website of the Serious Organised Crime Agency (SOCA), a UK police unit responsible for operations against serious and organized crime.

Assange, the founder and editor of whistleblower website WikiLeaks, has been ordered by Swedish authorities to be extradited from the UK where he had been under house arrest. Two women from Sweden have accused Assange of sex crimes, although he has yet to be charged.