Security has been stepped up in the Vatican, after intercepted communications revealed Islamist radicals planned to strike at the heart of the Roman Catholic church .

The Italian foreign security service revealed the details of a communication between two Arabic speakers that referred to a "demonstrative act, Wednesday, at the Vatican", intercepted by a foreign intelligence agency.

On Wednesdays and Sundays, Pope Francis I makes a public appearance on the balcony of St Peter's basilica before thousands of worshippers.

Checks by anti-terror police revealed that one of the men travelled through Italy eight months ago, leading to fears that they may be preparing to strike, reported Italian media.

Security has been stepped up for the pope's public audiences.

Plain clothes special operations officers with police dogs will patrol St Peter's Square, metal detectors will be installed, and hotels are being kept under surveillance, reports La Repubblica.

Vatican spokesman Father Federico Lombardi
Vatican spokesman Father Federico Lombardi Medol

Vatican spokesman Father Federico Lombardi downplayed the threat, saying that there had been no indications of a "particular threat or cause for concern".

Vatican attack threats

Some experts warn that the pontiff may have made himself a target for Islamic State militants, by voicing support for US air strikes against the group in Iraq, and his condemnation of the group's persecution of Christians and Yazidis.

In social media postings, Islamic State militants have spoken of wanting to spread the Islamic caliphate to Rome.

Fears were voiced for the pope's security on his visit to Albania next week, where it is believed he could be targeted by militants and terrorists returning from Syria or Iraq.

In Albania, the pope plans to travel in an open-topped vehicle, and meet well-wishers in the crowd.

In an interview with Italy's La Nazione daily this week, Iraq's ambassador to the Holy See, Habib Al Sadr, said "what has been declared by the self-declared Islamic State is clear. They want to kill the pope. The threats against the pope are credible.

"I believe they could try to kill him during one of his overseas trips or even in Rome," he continues. "There are members of Isil [Islamic State of Iraq and the Levant] who are not Arabs but Canadian, American, French, British, also Italians.

"Isil could engage any of these to commit a terrorist attack in Europe."