Islamic extremists suspected in a bomb attack in a Pakistani market that killed more than 100 people had also planned an attack against the Vatican in 2010 that was never carried out, an Italian prosecutor said Friday.

Wiretaps collected as part of an investigation into an Islamic terror network operating in Italy gave "signals of some preparation for a possible attack" at the Vatican, prosecutor Mauro Mura told a news conference in Cagliari, Sardinia. That included the arrival in Rome of a Pakistani suicide bomber, Mura said, who was "described as a kamikaze" — a type of suicide attack made infamous by the Japanese military in World War II.

“Kamikaze, crowded place, these are the clues,” the prosecutor said, adding that the pope at the time, Benedict XVI, was not a likely target.

The Pakistani eventually left Italy, Mura said, without explaining why. The Italian news agency ANSA reported that there were two suicide bombers and that they were warned off by their associates in Italy when police began executing search warrants in the case.

The Vatican downplayed the significance of the alleged plot.

"From what it appears, this concerns a hypothesis that dates from 2010 which didn't occur. It has therefore no relevance today and no reason for particular concern," the Rev. Federico Lombardi.

The news of the planned attack came as police said they arrested nine suspected extremists accused of plotting terror in Pakistan aimed at stopping that government's actions against the Taliban. Arrest warrants were being executed against some 20 suspects.

At the time of the suspected plot to bomb the Vatican, Pope Benedict XVI was still reeling from the effects in the Muslim world of a 2006 speech in Regensburg, Germany, in which he quoted a Byzantine emperor who characterized some of the teachings of the Prophet Muhammad as "evil and inhuman," particularly "his command to spread by the sword the faith."

While relations with the Muslim world were eventually repaired, tensions flared again in 2011 when Cairo's al-Azhar institute, the pre-eminent theological school of Sunni Islam, suspended interfaith talks with the Vatican after Benedict called for greater protections for Egypt's minority Christians.

More recently, Italian officials have made clear they take seriously the threat of the Islamic State group to conquer Rome and the seat of Christianity. Security has been beefed up at the Vatican and the head of the Swiss Guards has said they are ready but that they have no information about an imminent threat.

Pope Francis himself has said he realizes he may be a target but that he fears mostly for the innocent crowds who come to see him every time he's in public.

The investigation was launched in 2005, but Mura said it was slowed when news of the investigation leaked to the media, alerting the suspects that they were being watched.

Authorities said some of the suspects sought in the probe were responsible for "numerous bloody acts of terrorism in Pakistan," including the October 2009 explosion in a market in Peshawar in which more than 100 people died. That attack happened on the same day that then-Secretary of State Hillary Clinton visited the Pakistani capital, Islamabad, Mura noted.

One of the suspects arrested Friday had a construction business in Sardinia that participated in work for a Group of Eight summit planned for Sardinia but that was later moved to quake-stricken Aquilia, in Abruzzo to boost reconstruction.

Mura also said some of the suspects had very close ties to al Qaida leader Osama bin Laden, and that wiretaps included phone calls inquiring about his health.

Police said the aim of the terror network was to create an insurrection against the Pakistani government.

Additional reporting by Mashable.