Police across Europe and the United States have dismantled servers hosting media outlets linked to the Islamic State group "inciting terrorism in at least 30 languages", EU law enforcement authorities said Friday.

Authorities in Spain arrested nine "radicalised individuals" and servers were taken down in the US, Germany, the Netherlands, and Iceland, announced EU police force Europol and EU judicial body Eurojust.

"This week's joint operations are part of ongoing efforts and constant vigilance to tackle online terrorist propaganda and communications, including through social media," a joint statement said.

The channels targeted included a radio station, a news agency, and social media content in multiple languages.

The raids were the culmination of a year-long probe targeting propaganda networks "thereby limiting the ability of terrorist organisations to recruit, radicalise and mobilise recruiters online."

Authorities said some of the websites were also used to raise funds and coordinate attacks, with instructions on how to create explosives.

There was a "direct link" between the sort of propaganda being disseminated and an increased risk of attacks, Alberto Rodriguez Vazquez, from the Spanish police, told reporters.

Taking down the servers "denies the adversary its online battleground. It prevents the mobilisation of already terrorist members and the radicalisation of others," he added.