Sightseeing visits have been barred at Germany’s landmark cathedral in Cologne and Christmas Eve worshippers face security checks to get into midnight Mass as police responded to indications of a potential attack.

However, a top security official urged people not to shy away from holiday celebrations out of fear.

Churchgoers attended multiple services at the cathedral despite the ban on visits purely for sightseeing, a day after police descended on the cathedral and searched it with sniffer dogs.

With several dozen officers on duty outside, Auxiliary Bishop Rolf Steinhaeuser greeted those attending what he said 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.

Police at church
Police officers enter Cologne Cathedral ahead of a Christmas Eve Mass (dpa via AP)

They did not give further information, but the dpa news agency reported without citing a source that the threat came from an Islamic extremist group.

Police in Cologne said they were taking precautions over Christmas even though the information they had was for an attack on New Year’s Eve.

“Even if the reference was to New Year’s Eve, there are a lot of people in the area around the cathedral, today is Christmas Eve midnight Mass, it is one of the most visited cathedrals, the main train station is nearby,” police spokesman Wolfgang Baldes said while standing in front of the cathedral.

“There are a lot of people, and that’s why we said that if there was an indication, we would do everything necessary to protect people,” Mr Baldes added.

Cathedral Provost Guido Assmann said in an interview on the Cologne Archdiocese website domradio.de that halting sightseeing visits did not represent a big change since such visits are normally not allowed during services anyway, and services were scheduled throughout the day on Sunday.

Cologne’s towering cathedral, whose twin spires rise 515ft high, is a major tourist destination visited by some six million people a year.

Search of churchgoer
Churchgoers were searched at the entrance of Cologne Cathedral (dpa via AP)

It is home to the Shrine of the Three Kings, a gold- and silver-decorated casket said to contain the relics of the three wise men described in the New Testament as paying homage to the newborn Jesus.

Police and cathedral officials urged churchgoers planning to attend Mass on Sunday night to arrive early and not bring bags or purses.

At the same time, Herbert Reul, interior minister for the state of North Rhine-Westphalia, appealed to the public not to stay away.

“Caution is advised,” he said, but “we are not defenceless. Our agencies are using all available information to protect us as well as possible”.

Mr Reul added: “My appeal is, go to church, celebrate Christmas. Fear is the currency of terrorists. We should not make it more valuable.”

The European Union’s home affairs commissioner, Ylva Johansson, warned on 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.