O holy night? Security is heightened at church services at major cities across the world to prevent another terror attack

Security was heightened at church services in major cities across the world this evening in a bid to prevent an incident similar to the deadly truck attack on a Christmas market in Berlin.

Armed police officers stood outside the famous Notre Dame Cathedral in Paris as worshippers arrived for the Christmas Eve mass in the French capital.

Officers were seen patting people down and carrying out searches before they entered the 600-year-old building.

In France, Britain and Germany police increased their presence at tourist spots in major cities and other densely populated areas.

French officers stopped worshippers and searched them at the entrance of Notre Dame Cathedral in Paris on Christmas Eve

An armed police officer stands guard near the Notre Dame Cathedral as worshippers arrive for the Christmas Eve mass 

Two officers were photographed talking to each other outside the famous cathedral in the heart of Paris on Saturday night

Palestinian presidential security personnel gathered in front of the Church of Nativity, which is accepted by Christians as the birthplace of Jesus Christ, in Bethlehem, on Christmas Eve

The armed officers jump from a jeep as they are deployed at Manger Square in Bethlehem, on Christmas Eve on Saturday

It comes after Anis Amri, a 24-year-old Tunisian suspected of carrying out the truck attack which killed 12 people, was shot dead in a town near Milan early on Friday after he pulled a gun on police during a routine check.

In France, where Islamist militants killed 130 people in shooting and bomb attacks in Paris in November 2015, authorities said more than 91,000 policemen and soldiers would be deployed, with additional security measures being enforced at churches.

Meanwhile, armed guards patrolled the area around a church as Christians attended a Christmas Eve service in Bartalla, near Mosul, Iraq.

The officers were wearing camouflaged uniforms and were armed as they kept guard to offer security to worshippers on Saturday. 

And Palestinian presidential security personnel gathered in front of the Church of Nativity, which is accepted by Christians as the birthplace of Jesus Christ, in Bethlehem, on Christmas Eve.

Meanwhile, the UK is on its second-highest threat level, meaning an attack by militants is considered highly likely.

Police officers inspected people's bags at the entrance of the Cologne Cathedral in Cologne, Germany, on Christmas Eve 

An Iraqi security member stands guard as Christians attend a Christmas Eve service at the Mar Shimoni church in the town of Bartalla near Mosul

Iraqi security forces stand guard as Christians attended a Christmas Eve service at the Mar Shimoni church near Mosul

Italian police officers stand guard at a security check-point in a central street of Rome on Christmas Eve following the Berlin attack 

Pope Francis (pictured) leads the Christmas night Mass in Saint Peter's Basilica at the Vatican December 24

Pope Francis kisses a statue of baby Jesus as he leads the Christmas night Mass in Saint Peter's Basilica at the Vatican

Police there have increased security at a number of popular tourist attractions, including around Queen Elizabeth's London residence, Buckingham Palace. 

Rome authorities have banned vans or trucks from entering the city centre and anti-terror police wearing masks and wielding machine guns set up roadblocks on routes leading to famous tourist sites or areas where crowds traditionally gather.

At the Vatican, where Pope Francis was due to celebrate Christmas Eve Mass in St. Peter's basilica on Saturday evening, police cars and military jeeps stood about every 100 metres along streets leading to the Vatican.

Security was also stepped up in central Milan and other Italian cities, particularly near major churches where the faithful were attending Christmas services.

Turkish police check the grounds of the Saint Anthony of Padua Church prior to the start of the Christmas Eve mass in Istanbul

A Turkish security officer checks the purse of a woman a she enters Saint Anthony of Padua Church prior to the start of the Christmas Eve mass

A Pakistani security officer stands guard outside the Saint Anthony's church during a midnight service on Christmas eve in Lahore, Pakistan

Children were photographed trying to grab ornaments from a tree in the old city of Damascus, Syria, on Christmas Eve

People took selfie photos near a Christmas tree outside the state-approved Xuanwumen Catholic Church, otherwise known as the South Cathedral in Beijing

People gathered near a Christmas tree close to damaged buildings during Christmas Eve in the Al-Hamidiyah neighbourhood in the city of Homs, Syria

People participated at a Christmas Eve mass in Sent Antuan church, the largest church of the Roman Catholic Church in Istanbul