A major counter-terror operation took place in the German city of Cologne on Saturday after security services in Austria, Germany, and Spain received intelligence of an Islamist terrorist cell’s plans to carry out several attacks across Europe over the Christmas period.

Sniffer dogs trained to detect explosives were deployed at Cologne Cathedral after a specific threat was received regarding the Gothic landmark as authorities sought to ensure that no devices had already been planted at the location.

“Due to a warning of danger for Cologne Cathedral, the Cologne police will take special protective measures from this evening,” a spokesperson for the city’s police said, as cited by the German tabloid Bild.

“The police will not comment on details of the available findings due to ongoing investigations by the police state security service,” they added.