Mullah Krekar after his release from Norwegian prison in January 2015 | Audun Braastad/AFP/Getty Images) Busted jihadist network plotted to snatch diplomats Arrests in ‘Operation Jweb’ include Ansar-al Islam founder Mullah Krekar.

Police in Italy, Britain, Norway and Finland on Thursday arrested 15 members of a jihadist network linked to Islamic State and al Qaeda who are suspected of planning attacks and kidnappings targeting EU diplomats, officials and journalists to bargain for the release of jailed colleagues.

Italy's anti-terrorism chief Giuseppe Governale, announcing the details of "Operation JWeb," called it "the most important international police operation in Europe in 20 years."

The detainees included major names on the global jihadi network, foremost among them Mullah Krekar, an Iraqi Kurd who co-founded Ansar al-Islam, an armed Sunni Islamist group linked to al Qaeda and ISIL.

Since 1991, Mullah Krekar has lived in Norway where he has had an expulsion order pending for years because of the threat he poses to national security — the scale of which was made even clearer by phone taps released by police when they announced the arrests. Oslo has so far refrained from expelling Krekar because he could potentially face the death penalty in Iraq.

"He's a very significant jihadi creature, one of the big names," said Raffaello Pantucci, counter-terrorism expert at the Royal United Services Institute in London.

Italy's Carabinieri police said arrest warrants had been issued for 17 people, of whom 16 are Kurdish and one is a Kosovar. The arrests Thursday morning included seven men in Italy, four in the U.K., and three in Norway including Krekar. Police in Finland, Switzerland, Germany, Greece and the United States were also involved in the operation.

The five-year operation was coordinated by Eurojust, an EU agency for judicial action against organized crime, and kicked off after initial investigations into the jihadist website www.jarchive.info.

The Carabinieri said in a statement that Mullah Krekar was the leader of an international terrorist organization which goes by two names — "Rawti Shax" and "Didi Nwe" — and which acts as "a network to recruit volunteers for the conflict and facilitate their travel to war zones."

According to Pantucci, the JWeb police operation "goes deep and has disrupted the network of the group. You are never going to be able to shut it completely down but I think that, given the length of the investigation, they sort of scooped everyone."

Norway to become Lebanon

Police released excerpts from tapped phone conversations between the arrested members of the network which included talk of violent recriminations for Mullah Krekar's previous detention in Norway.

"If [Mullah Krekar] is annihilated, Norway is going to become Lebanon. You will see how the bombs go off — boom, boom, boom at the police," reads an excerpt from one of the phone taps, which also included conversations about potential kidnap targets among the Norwegian community abroad.

In a phone tap recorded two days after Krekar was arrested in Norway in 2012, on charges of incitement, three members of the network discussed potential kidnap targets, whom they would use to negotiate for his release.

"The solution is to attack an embassy in Baghdad or in the south or in Iran, also in Arab countries, but not in Europe, and have two or three 'guests'," said Abdul Rahman Nauroz, leader of the Italian cell of Rawti Shax and a veteran Ansar al-Islam fighter.

"I think this is a good idea, we should capture them as 'asir' (prisoners of war in Arabic)," replied Abdul Salih Ali, the ideologue of the network, who was arrested in Italy. "They'll never go back to Norway as long as they live."

In another conversation between Nauroz and Hamad Bakr, who was arrested in Britain on Thursday, the talk is about securing Mullah Krekar's release by kidnapping a U.K. ambassador: "I say the embassy, the British embassy, England is big, kidnapping the head of the embassy and putting him in a basement."

Magnus Ranstorp, an expert on Islamic terrorism at the Swedish National Defense College, said the impact of the operation "is going to be huge." He described Rawti Shax as very ideological organization, with a sketchy structure and a "strong underground network that never makes official communiqués and never claims responsibility for any terrorist acts in the EU or abroad."

As for Mullah Krekar, Ranstorp said the serious nature of the charges against him would make it very difficult for him to avoid jail.

This story was updated to include details of kidnapping plans.