Pope Francis at Redipuglia Military Sacrarium
Pope Francis walks inside the Austro-Hungarian cemetery at Fogliano in Redipuglia September 13, 2014. Pope Francis marked the centenary of World War One (WWI) at the Redipuglia Military Sacrarium with a mass. REUTERS/Stefano Rellandini (ITALY - Tags: RELIGION ANNIVERSARY CONFLICT MILITARY) Reuters/Stefano Rellandini

A stranger with the Islamic State flag shouted threats of killing "Christians and their children" at churchgoers in Sydney on Tuesday.

The stranger drove a car past Our Lady of Lebanon Church at Harris Park and threatened to "kill the Christians" and their children as well. According to witnesses, he had a triangular flag which resembled that of the Islamic State. The flag was hanging out of the car window, The Sydney Morning Herald reported.

A priest confirmed the threats and said that the churchgoers had been scared. "They were strong words and people were scared of what they saw," he said. Rosehill police Inspector Brian Jackson also confirmed the death threats made near the church. Police were called to the church on Wednesday before the mass at 7 o'clock in the evening. Hundreds of people participated in mass in the Our Lady of Lebanon Church while police officers patrolled the area.

The Vatican was earlier warned by Habeeb Al-Sadr, an Iraqi ambassador, that Pope Francis was at risk of being assassinated by the Islamic State terrorists. The 77-year-old is apparently vulnerable when he visits Albania on Sunday, Sept 21. He will also be vulnerable when he visits Turkey in November, the ambassador informed. The ambassador confirmed that the death threats against the pontiff were "credible," The Independent reported. The Islamic State militants earlier claimed to plant their black flag on St Peter's Basilica.

Al-Sadr told Italian daily "La Nazione" that the pontiff was targeted after he had spoken in favour of the United States and its allies to conduct a mission against the Islamic State in the Middle East. "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," he said, "I believe they could try to kill him during one of his overseas trips or even in Rome. There are members of Isil who are not Arabs but Canadian, American, French, British, also Italians. Isil could engage any of these to commit a terrorist attack in Europe."

The pope is going to celebrate Mass in Albania's capital, Tirana, on his visit there in Sunday. He also has plans to move around in his open Popemobile.

Contact the writer: s.mukhopadhyay@ibtimes.com.au