ROME — The Italian authorities arrested nine people on Friday and said they were part of a Qaeda-linked terrorist cell based on the island of Sardinia that the police have been watching for years.

The group plotted attacks in Pakistan, and at one point planned to strike the Vatican, as part of a “big jihad in Italy,” one police official said. Another nine suspects were still being sought.

Wiretaps collected over the course of seven years of active investigation found “signals of some preparation for a possible attack” at the Vatican in March 2010, Mauro Mura, the chief prosecutor of Cagliari, Sardinia, told reporters on Friday. Those wiretaps revealed the presence in Rome of a Pakistani man “described as a kamikaze,” Mr. Mura said, meaning someone who “was destined for martyrdom.”

Mr. Mura said the planned attack was not necessarily aimed at the pope of the time, Benedict XVI, but rather at the throngs of tourists and pilgrims who fill St. Peter’s Square twice a week to hear the pope speak. “Kamikaze, crowded place, these are the clues,” he said.