A truck plowed into a Christmas market in Berlin, Germany on Monday, killing nine people while injuring at least 50 others, according to police.
The driver is in custody, according to German media.
Police believe the attack was deliberate, the BBC reported.
The German-based Berliner Morgenpost shared a video to its Facebook page showing stands knocked over with sirens audible in the background.
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The Islamic State has encouraged its followers to use large trucks as a weapon to inflict mass casualties.
This past summer, a lone-wolf attacker killed 86 people in Nice, France, after driving a cargo truck through crowds celebrating Bastille Day on the Promenade des Angalis. ISIS called the assailant a "soldier."
The U.S. State Department issued a travel alert last month urging citizens to be vigilant while attending holiday festivals, events, and outdoor markets in Europe due to a heightened risk of terrorist attacks.
The State Department cited "credible information" suggesting that ISIS, al Qaeda, and affiliates were planning terrorist attacks against European targets, particularly as the holiday season approaches.
"U.S. citizens should also be alert to the possibility that extremist sympathizers or self-radicalized extremists may conduct attacks during this period with little or no warning," the State Department wrote on Nov. 21. "Terrorists may employ a wide variety of tactics, using both conventional and non-conventional weapons and targeting both official and private interests."
This post will be updated as more information becomes available.