Italian police issued six arrest warrants Thursday for people suspected of plotting to join the Islamic State group. Three of the suspects were plotting attacks on the Vatican and the Israeli embassy in Rome, Reuters reported.

“I swear I will be the first to attack them in this Italy of crusaders, I swear I’ll attack it, in the Vatican, God willing,” one man said, according to a transcript of a wire-tapped conversation released by Italian officials. Another recording revealed the same man said he had contacted an Albanian man in order to get a gun so he could target the Israeli embassy in Rome.

Officials across Europe have stepped up security in the wake of major terrorist attacks in Paris and Brussels. The Islamic State group, also known as ISIS, took responsibility for both attacks. The November attacks in Paris left 130 people dead and hundreds injured while attacks in Brussels in March left 32 people dead and hundreds injured.

American officials said Monday that ISIS was operating cells throughout Europe in countries including Germany, Britain and Italy.

“That is a concern, obviously, of ours and our European allies,” said James R. Clapper Jr., the director of national intelligence, when asked about the terror group’s activity across Europe, the New York Times reported.

“We continue to see evidence of plotting on the part of ISIL in the countries you named,” he said, using another acronym for the terrorist group. Clapper said American officials have been working with their European counterparts to share intelligence and encourage greater cooperation across European borders.

Italian officials said four of the six suspects were arrested Thursday while the location of a Moroccan man and his Italian wife was still unknown. Officials said the couple had left Italy last year to travel to either Iraq or Syria where ISIS controls territory.

“The new aspect here is that we are not talking about a generic indication [of an attack] but a specific person being appointed to act on Italian soil,” said Milan prosecutor Maurizio Romanelli.