President-elect Donald Trump vowed a month before he takes office, to wipe "terrorists" off the face of the Earth, after a series of high-profile attacks in Germany, Turkey and Switzerland.
German police have so far spoken of a possible terror attack after a truck plowed through a crowd, killing at least 12 and injuring dozens more in scenes reminiscent of July's deadly truck attack in the French city of Nice.
But still, Trump condemned the "horrifying terror attack."
"ISIS and other Islamist terrorists continually slaughter Christians in their communities and places of worship as part of their global jihad," he added, referring to the Islamic State group.
Trump then promised: "These terrorists and their regional and worldwide networks must be eradicated from the face of the Earth, a mission we will carry out with all freedom-loving partners."
In Ankara, a policeman shot dead Russia's ambassador to Turkey. Trump called the gunman a "radical Islamic terrorist."
The shooting, during which the gunman shouted "Aleppo" and "Allahu akbar" (God is great), occurred on the eve of a key meeting in Moscow between the Russian, Turkish and Iranian foreign ministers on the Syrian conflict.
Protesters in Turkey have held Moscow responsible for human rights violations in Aleppo, with thousands protesting outside the Russian consulate in Istanbul.
Turkey and Russia stand on opposite sides of the Syria conflict with Ankara backing rebels trying to topple Moscow's ally President Bashar al-Assad.
But the rhetoric has warmed considerably since a reconciliation deal was signed earlier this year and a Russian and Turkish-brokered accord has helped the evacuation of citizens from Aleppo in the last days.
As a billionaire real estate investor, Trump has curried favor with Moscow through his business dealings over the decades.
His pro-Russia views came under increasing scrutiny in 2015 as he opened his ultimately successful White House campaign, as he has brushed off reports of brutality and repression by Vladimir Putin's Kremlin.
Those ties are coming under fire after US intelligence agencies found that Russia had tried to sway the US election via a cyber hack.
At the same time, relations between the former Cold War foes are at a very low point.
In Switzerland, a man burst into a Muslim prayer hall, shooting and wounded three men.
Witnesses had described the shooter as a man aged around 30 wearing dark clothes and a dark woollen cap.
A number of Swiss mosques, including one near Zurich and the main one in Geneva, have in recent months been accused in media of allowing or encouraging the radicalization of their worshippers, especially the younger members of their congregations.
"Today there were terror attacks in Turkey, Switzerland and Germany - and it is only getting worse. The civilized world must change thinking!" Trump concluded on Twitter.