During a campaign-style rally in Florida on Saturday, Mr Trump pointed to incidents in Germany and Sweden as a justification for his controversial travel ban temporarily denying entrance to refugees and citizens of seven predominantly Muslim countries.
While his remarks about Germany were in reference to the Berlin Christmas market attack, his specific reference to what happened “last night” in Sweden, left officials, journalists and members of the public wondering if they had missed something.
“When you look at what’s happening in Germany, when you look at what’s happening last night in Sweden — Sweden!“ he said.
”Who would believe this? Sweden! They took in large numbers, they’re having problems like they never thought possible.”
Swedish Foreign Ministry spokeswoman Caterina Axelson said the Government is not aware of any “terror-linked major incidents”.
Ms Axelson told Swedish news agency TT that Stockholm is now demanding an explanation.
“Our embassy in Washington has been in contact with the US foreign affairs office to get clarification. We’re of course wondering [what he referred to].
“Let’s see if we get an answer”.
Sweden’s security police spokesman Karl Melin said nothing had occurred that would cause them to raise “the terror threat level” in the country.
Former Swedish Foreign Minister Carl Bildt was also left baffled by the President’s comments.
“Sweden? Terror attack? What has he been smoking? Questions abound,” he tweeted.
Twitter ran wild with speculation as to what Mr Trump could have meant, with suggestions including the fact that it had snowed or that herds of reindeer had crossed the border.
A series of hashtags were coined, including #lastnightinSweden and #jesuisikea.
Mr Trump did not elaborate during the rally as to which Swedish incident he was referring to and has not issued any comment or tweeted on the matter since.
The Trump administration faced a similar backlash after the President’s top aide Kellyanne Conway referenced the “Bowling Green Massacre,” a non-existent attack, to defend the President’s travel ban.
Ms Conway later said she misspoke.