ROME • The police in six European countries arrested at least 15 suspected members of an extremist militant group that was planning attacks in northern Europe and the Middle East, the Italian authorities said yesterday. 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 targets or the timeframe.

The early morning raids targeted the Rawti Shax group, which the police said was a Kurdish Sunni Muslim group dedicated to overthrowing the government of Iraq's Kurdistan region and replacing it with rule by syariah.

Italy's national Carabinieri police led the investigation, with security forces in Italy, Britain, Norway, Finland, Germany and Switzerland taking part in yesterday's swoop. "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. One of those wanted was believed to be in Iraq, while it was not yet clear whether another suspect had been found in Switzerland.

All of them face international terrorism charges, the Carabinieri police said in a statement. Among those detained was Mullah Krekar, the one-time leader of the Ansar al-Islam militant group.

He was served the 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.

Krekar went to Norway as a refugee in 1991 and had earlier been deemed a threat to national security. However, the Norwegian authorities did not expel him to Iraq because the authorities there could not guarantee he would not be executed.

Meanwhile, Turkish police detained 11 suspects in helicopter-backed raids targeting Islamic State in Iraq and Syria (ISIS) militants across Istanbul, the state-run Anadolu Agency reported yesterday, just days ahead of a G-20 summit being held in the country. The raids were part of a series of operations against suspected militants in Turkey, where security is being tightened ahead of the world leaders' summit.

Last week, the police detained 20 people suspected of links to ISIS in the southern resort province of Antalya, where the G-20 summit is being held on Sunday and Monday.

The anti-terror squad police carried out simultaneous raids on more than 20 addresses in various districts of Istanbul, Anadolu said.

AGENCE FRANCE-PRESSE, REUTERS