Despite the security concerns currently hounding major cities in the West following the gruesome terrorist attacks in Paris last Friday that left at least 129 people dead, fear should not cause churches to close their doors on people who truly seek Christ, Pope Francis said.

The head of the Roman Catholic Church said during his St. Peter's Square address that Catholic churches should always be open.

"Please, no armored doors in the church, everything open," he said. "There are places in the world where doors should not be locked with a key. There are still some, but there are also many where armoured doors have become the norm."

The 78-year-old pope said: "We must not surrender to the idea that we must apply this way of thinking to every aspect of our lives," the Pope added. "To do so to the Church would be terrible."

He explained that Christians have the responsibility to open up their hearts, and therefore their doors to everybody in need, and this is why the church must always be open.

"As guardians of that door, we in the Church are called to be welcoming to all who seek to enter the fold of the Good Shepherd. May the doors of our Christian homes be signs and symbols of the door of God's mercy, a door ever open to all who knock and desire to meet Jesus," he said.

Pope Francis did not specifically mention the Paris attacks during his address even as security measures have been heightened in Rome following attack threats made by the Islamic State (ISIS).

Around 700 extra Italian troops have been deployed in Rome. It was announced that the city's airspace will be closed to drones throughout the Catholic jubilee year, which will start on Dec. 8.