UPDATE: 3:32 p.m. EST - ABC News confirms earlier reports that 40 people were killed.

At least 40 people were killed and over 100 others were injured in a shooting and explosion at Moscow's Crocus City Hall -- one of the biggest shopping and entertainment complexes in Russia -- on Friday evening, according to the Russian Foreign Security Service.

Russia's foreign ministry called the shooting and explosion a "terrorist attack."

More than 70 ambulance teams were sent to the sight of the attack, the governor of the Moscow region reported.

Videos show a gang of men armed with AK-style machine guns walking through the Crocus City Hall, an entertainment venue in Moscow. The videos are extremely graphic and show the men casually walking through the venue as they shoot civilians who are trying to hide.

From The Guardian:

Moscow mayor Sergei Sobyanin called the attack a "great tragedy." At least 50 ambulances had been dispatched to the site of the attack.

"The attackers presumably opened fire at the entrance to the building during a concert, using automatic weapons, and then a fire began in the building," said emergency services. Authorities said that up to five people took part in the attack.

Here is the most tame videos I could find that don't include blood or bodies.

[Warning: Violence]

The venue was then set on fire.

On March 8th, the United States warned Americans in Moscow of an impending threat of internal attack.

The U.S. Embassy in the Russian capital said it was "monitoring reports that extremists have imminent plans to target large gatherings in Moscow, to include concerts, and U.S. citizens should be advised to avoid large gatherings over the next 48 hours.

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