The Islamic State says it is responsible for a Friday shooting that killed at least 133 people after gunmen stormed a concert hall in a suburb of Moscow, per The New York Times.

The big picture: Russia's Federal Security Service (FSB) said it opened a terrorism investigation into the attack at Crocus City Hall. The attack included explosions that started a massive blaze in the concert hall, which could accommodate over 6,000 people.

The latest: U.S. officials have confirmed the Islamic State's claim, which was originally posted by its affiliated news agency on the messaging app Telegram and reported by The New York Times.

Russian state media outlet TASS reported that shopping centers in St. Petersburg were closed and the entire Leningrad region was placed under high alert.

• TASS further reported that the second floor of the concert hall was almost destroyed by the fire.
• Russia's National Guard said a search for the gunmen was ongoing.

What they're saying: The Office of the Ukrainian President of Volodymyr Zelensky said his country was not involved.

• White House National Security Communications Adviser John Kirby in a press conference Friday expressed sympathy for victims of "this terrible, terrible shooting attack" and said there was no indication Ukraine, or Ukrainians, were involved.
• Kirby said the U.S. did not have prior knowledge and that he believes the previous warning from the embassy was not related to Friday's attack.

Context: The U.S. Embassy in Moscow sent out a warning around two weeks ago for U.S. citizens to avoid crowds because "extremists have imminent plans to target large gatherings in Moscow," including at concerts.

• The same day the embassy issued that warning, the FSB, the successor to the Soviet-era KGB, said it thwarted an attack on a Moscow synagogue by an Islamic State cell.
• The security service said it had seized firearms, ammunition and components for manufacturing an improvised explosive device after preventing the attack.
• On Tuesday, Russian President Vladimir Putin dismissed terrorism warnings from Western embassies in a speech during the FSB spy service's annual meeting, calling them "blackmail" meant to "intimidate and destabilize" Russia.

Zoom out: The attack comes just days after Putin solidified his rule over the country throughout the remainder of this decade and into the 2030s.

• It also occurred the same day that the Kremlin for the first time used the word "war" to refer to its unprovoked invasion of Ukraine. Previously, it had been referring to the invasion as a "special military operation."

Editor's note: This story has been updated with the latest news.