Italian police were arresting 18 people on Friday suspected of belonging to an armed group linked to Al Qaeda who were plotting attacks on the Vatican as well as in Pakistan and Afghanistan.

Some of the suspects, who are all Pakistanis and Afghans, were arrested in early morning raids across Italy.

Police burst into the home of the group's suspected spiritual leader, in the northern city of ­Bergamo, a video released by them showed.

Though the suspects were plotting attacks mainly in their native countries, phone taps suggest the Vatican was also a target, said Mauro Mura, chief prosecutor of the Sardinian city of Cagliari, where the group based its headquarters.

In the tapped conversations, the suspects discuss "a big jihad in Italy," added Mario Carta, head of the police unit on the case. They reference the word "baba," which could mean the pope, Carta said.

"We don't have proof, we have strong suspicion," that the Holy See was a possible target, he added.

Vatican spokesman Federico Lombardi said the hypothetical attacks were in the past, and that the new disclosures were not a matter for concern.

Italy, like other European countries, has been on heightened alert for possible terrorist schemes in the wake of the January attack on French satirical magazine Charlie Hebdo.

European capitals are particularly worried about possible "sleeper" militants, apparently living normal lives in their countries, who may at some point in the future be activated to stage attacks at home or abroad.