Europe has gone on high security alert just days before Christmas, after terror attacks hit three cities in the same evening, while news that the perpetrator of the deadly Berlin assault might still be armed and at large sent fresh jitters across Germany.
German Chancellor Angela Merkel faced pressure from her Bavarian allies, who urged her to review the country's immigration and security policies, after police arrested a Pakistani asylum seeker who was thought to have rammed a truck into a Berlin Christmas market on Monday night, killing 12 and injuring dozens more.
But at a press conference yesterday afternoon, the city's police chief said they may have arrested the wrong man. He appealed for witness accounts, as well as pictures and videos of the attack, and urged Berliners to remain calm.
The Die Welt newspaper quoted a senior police source as saying: "The true perpetrator is still armed, at large and can cause fresh damage."
In an earlier nationally televised address, Dr Merkel said the attack was "particularly repugnant" if it was the act of a refugee, and that the German authorities were working on the basis that it was carried out by a terrorist.
In Zurich, police have identified a 24-year-old Swiss man who was interested in the occult as the person behind the shootings that injured three worshippers at an Islamic centre on Monday evening. The man, who the police did not name, had no apparent links to Islamic radicalism, and was thought to have killed another man on Sunday. He was believed to have killed himself after the attack on the Islamic centre.
Turkish police have also held six people for questioning over the assassination of the Russian Ambassador at a photography exhibition in Ankara on Monday night. They included the parents and other relatives of the gunman, Mevlut Mert Altintas, an off-duty riot police officer. Altintas shot Ambassador Andrei Karlov multiple times and was later killed by police at the scene.
Russian President Vladimir Putin called Mr Karlov's assassination a "provocation" aimed at derailing relations between the two countries, and vowed to continue jointly fighting terrorism, saying "the bandits will feel this".
The spate of attacks, although seemingly unrelated, has put countries across the continent on heightened security.
French President Francois Hollande said yesterday that his country was under a "high level of threat" from terrorists following the Berlin carnage. It already has a large-scale security operation in place after coming under terrorist sieges over the past two years.
Police forces have also beefed up security at Christmas markets across Britain, as well as shopping malls, tourist hot spots and transport hubs.
Before Monday's attacks, more than 200 undercover special forces soldiers had already been deployed to guard Britain's streets against possible terror attacks during the festive season.
The Singapore authorities have also said there will be greater police presence and increased checks on bags during the Christmas and New Year period.
Yesterday, Belgian police also arrested a man in the neighbourhood of Schaerbeek who allegedly made terror threats and was suspected of possessing weapons and explosives.
Belgium has been on high alert since suicide bombers hit the capital city's airport and a metro station in March this year, killing 32 people.
SEE TOP OF THE NEWS