Several European countries have tightened security measures for Christmas over fears of possible terrorist attacks. French Interior Minister Gerald Darmanin instructed police and gendarmes to increase their presence at churches across the country "to protect the Christian faithful who will be gathering for the Christmas festivities this evening and tomorrow morning," he said Sunday on X, formerly known as Twitter. In neighboring Germany, authorities also stepped up their security efforts. "[Police] will be doing everything we can tonight to ensure the safety of visitors to the cathedral on Christmas Eve," Cologne Police Chief Michael Esser said in a statement Saturday, adding that all visitors to the city's famous cathedral will be subject to security check at the entry. Police searched the cathedral with sniffer dogs on Saturday night following report that Islamist groups are planning an attack on the church for either Christmas Eve or New Year, according to the statement. Police advised visitors against carrying any bags with them to avoid delays at security checks. Police in the Austrian capital of Vienna increased its security presence at Christian events for Christmas too, due to "an increased risk in Austria during the Christmas holidays," it said in a statement Saturday. "As terrorist actors throughout Europe are calling for attacks on Christian events in this context - especially around December 24th - the security authorities have increased the corresponding protective measures in public spaces in Vienna and the federal provinces," the statement said. The nature of the threat is unclear, but the European Commissioner for Home Affairs Ylva Johansson warned earlier this month that with war between Israel and Hamas ongoing there was a "huge risk" of attacks. Last week four alleged Hamas members suspected of plotting terror attacks on European soil were arrested by German and Dutch authorities. — CNN