Italian police issued arrest warrants on Thursday for six people suspected of conspiring to join Islamic State, and court documents said three of them had been discussing possible attacks on the Vatican and the Israeli embassy in Rome.
Four of the suspects - a couple living near Lake Como, a 23-year-old-man and a woman, all of them Moroccans - were detained in Italy on Thursday, Milan prosecutor Maurizio Romanelli told a news conference.
The other two - a Moroccan man and his Italian wife - left Italy last year, traveled to Iraq and Syria and are still on the loose, Romanelli added.
Italy has not suffered the kind of deadly Islamist attacks that hit France and Belgium, but authorities have arrested a number of people suspected of planning assaults.
Transcripts of wire-tapped phone conversations between three of the suspects, contained in the arrest warrant and seen by Reuters, mentioned the possibility of an attack against the Vatican and the Israeli embassy in the Italian capital.
"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 of the arrested men is quoted as telling the man on the run in the transcript.
In a separate conversation with another of the suspects arrested on Thursday, the same man said he wanted to hit the Israeli embassy in Rome and had contacted an Albanian man to get a gun.
"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," Romanelli said.
"Rome attracts attention because it is a destination for Christian pilgrims," the prosecutor added.
A lawyer appointed to represent two of the suspects declined to comment, saying he was waiting for court papers.
A 22-year-old Somali asylum seeker who worked as an imam was detained in southern Italy last month on suspicion of planning an attack in Rome.