The 13 suspected members of a jihadist group arrested in raids across Europe were allegedly recruiting foreign fighters to be sent to Iraq and Syria.
The early-morning raids in Finland, Germany, Italy, Norway, Switzerland and the UK targeted the Rawti Shax group, which police said was a Kurdish Sunni Muslim association dedicated to overthrowing the government of Iraq's Kurdistan region.
It seeks to establish a caliphate there, installing rule by sharia, the Islamic code of law and morals.
Rawti Shax, which means "The New Course", also has cells in Greece, Sweden, Iraq, Iran and Syria, according to the European Union's judicial co-operation unit Eurojust.
"This was an incredibly difficult and complicated investigation that has been going on for five years," said prosecutor Franco Roberti, the head of Italy's anti-mafia and anti-terrorism unit.
A total of 17 arrest warrants were issued, almost all for Iraqi Kurds, and 15 suspects were picked up immediately.
All of them face international terrorism charges, the Carabinieri said in a statement.
As well as the arrests, authorities in the various countries searched 26 premises and seized electronic devices and documents, Eurojust said in a statement.
Among at least 15 suspected members of the militant Islamist group arrested was the group's imprisoned leader, Mullah Krekar.
Italian police said the group was also planning attacks in Norway and the Middle East, with the aim of securing Krekar's release by Norway.
They said the militants planned to strike Norwegian and British diplomats in the Middle East and politicians in Norway, but gave no further information about the potential targets or the time frame for any attacks.
Krekar, an Iraqi Kurd, is serving an 18-month sentence for making threats and encouraging others to commit criminal acts.
Krekar went to Norway as a refugee in 1991 and had earlier been deemed a threat to national security. However, Norwegian authorities did not expel him to Iraq because authorities there could not guarantee he would not be executed.
Krekar received his arrest warrant in a prison in Norway, where he was already serving an 18-month term for making death threats against a Kurdish man and encouraging others to commit criminal acts in a TV interview.
Police in Oslo said there had never been a "concrete or acute threat" against any Norwegian citizens or interests.
General Giuseppe Governale of the Italian Carabinieri's Special Operations Group, which launched the investigation, told journalists in Rome that the operation constituted "the most important police operation in Europe in the last 20 years".
It had "dismantled an integrated cell" that had developed "on the 'dark web', little-known [internet] platforms that we have managed to penetrate", he said.
The cell, the general alleged, "was about to continue sending many other jihadists abroad; it was about to carry out attacks, including suicide bombings, to try to free their chief, Mullah Krekar".
The attacks could have targeted Norwegian and British diplomats, Italian media cited General Governale as saying.
However, Eurojust, British police, and the Norwegian Police Security Service could not confirm the existence of a plot against diplomats.
Italy said it would now seek to extradite Krekar.
- BBC, AFP