Christians around the world were striving on Christmas Eve to put aside the worries and fears of an unsettled, war-torn world as they prepared to celebrate the birth of Jesus of Nazareth.

Before leading Sunday Mass at St. Patrick's Cathedral in New York City, Cardinal Timothy Dolan reminded congregants to keep war-torn parts of the Middle East in their Christmas prayers.

"As we anticipate Christmas, our hearts always go to the holy land," he said, referring to parts of Israel and the Palestinian territories. "The holy land is under a cloud, the holy land is suffering, the holy land is filled with violence and hatred and retribution. And this dulls and threatens to suffocate the joy of Christmas."

Believers in Syria gathered in a country still suffering from the aftermath of a long civil war and suffocating economic blockade. Despite festive lights and Christmas decorations adorning houses and shopfronts in the capital Damascus, events in Gaza and ongoing battles in parts of the country have left the holiday atmosphere subdued.

In Yabroud, a city north of Damascus, worshippers gathered in the St. Constantine and Helen Cathedral to enjoy Christmas carols sung by the Joy Choir from Damascus. "Everyone should try, with what the Lord has given them, to spread joy in order to help end this sorrow," said Fadi Homsi, a member of the choir.

Prosperous, mostly secular Europe marked the holiday in historic cathedrals and brightly lit holiday markets, with an undertone of tension spread by the war in Gaza and by one even closer to home in neighbouring Ukraine. Wages that haven't yet caught up with inflation dampened the mood during the pre-holiday shopping and dining season.

Sightseeing-only visits were barred at Germany's landmark cathedral in Cologne and Christmas Eve worshippers faced security checks to get into midnight Mass there Sunday as police responded to indications of a potential attack. Still, officials urged people not to shy away from holiday celebrations out of fear.

Auxiliary Bishop Rolf Steinhaeuser greeted people attending services with a relaxed smile and an expression of thanks for police security efforts, a day after police descended on the cathedral and searched it with sniffer dogs. With several dozen officers on duty outside, he said it was "probably the most secure church service in all of Germany."

In Austria, police said they also were stepping up security around Vienna's churches and Christmas markets, apparently responding to the same intelligence about a potential threat. They did not give further information, but the dpa news agency reported without citing a source that the threat was from an Islamic extremist group.

Cologne's towering cathedral, whose twin spires rise 157 metres high, is a major tourist destination visited by some 6 million people a year. It is home to the Shrine of the Three Kings, a gold- and silver-decorated casket said to contain the relics of the wise men described in the New Testament as paying homage to the newborn Jesus.

The European Union's home affairs commissioner, Ylva Johansson, warned December 5 that Europe faces a "huge risk of terrorist attacks" over the Christmas holidays due to fallout from the war between Israel and the Palestinian militant group Hamas. Johansson provided no details about any police or security information that might have led to her warning.

Ukraine is preparing to officially mark Christmas as a state holiday on December 25 for the first time after moving the date in line with countries in Western Europe. President Volodymyr Zelenskyy signed legislation in July moving the holiday to December 25 from January 7, when it is observed by the Russian Orthodox Church and also by one of Ukraine's two competing Orthodox churches. Some Eastern Orthodox churches continue to use the ancient Julian calendar, under which Christmas falls 13 days later.

A note attached to the law said its goal was to "abandon Russian heritage" and cited "the desire of all Ukrainians to live their lives with their own traditions, holidays."

"The nights before Christmas are the longest of the year. However, the day has already begun to lengthen and the light has begun to prevail. The light grows stronger. Darkness will eventually lose. Evil will be defeated," Zelenskyy said in a video address Sunday.