Investigators in Europe and the US say they dealt a blow to terrorist propaganda and communication online, Europol said in a statement issued on Friday.
They said they shut down servers and websites that had links to the extremist militia organization Islamic State in particular.
Spain's judicial authorities detained nine suspects and secured masses of data, in operations coordinated by Europol and EU judicial authority Eurojust.
Europol said the servers supported media connected to Islamic State, including radio stations, a news agency and social media content.
These were disseminating terrorist instructions and slogans in more than 30 languages, Europol said.
Investigators also shut down 13 websites and four servers in 10 countries. The websites enabled terrorists and other violent extremists to spread pop propaganda and incite violence, Europol and Eurojust said.
They also published instructions for the use of explosives, collected funds, coordinated attacks and recruited new members.