Moscow-

Russian authorities have arrested four suspects as a suburban Moscow concert hall where gunmen opened fire on concertgoers on Saturday was reduced to charred, smoldering ruins, killing more than 130 people in the attack. President Vladimir Putin claimed they were captured while fleeing to Ukraine.

Kyiv has strongly denied any involvement in Friday’s attack on Krasnogorsk’s Krokos Town Hall concert hall, for which the Islamic State group’s Afghan affiliate claimed responsibility.

Putin did not mention Islamic State in his address to the nation, and Kyiv has accused him and other Russian politicians of falsely linking Ukraine to the attack to fan Russia’s war in Ukraine, which recently entered its third year.

U.S. intelligence officials confirmed the Islamic State affiliate’s claims.

“ISIS bears full responsibility for this attack. Ukraine had no involvement,” National Security Council spokesperson Adrienne Watson said in a statement.

Watson said the United States shared information with Russia in early March about planned terrorist attacks in Moscow and issued a public warning to Americans in Russia.

Putin said authorities detained a total of 11 people and injured more than 100 people in the attack. He called it a “bloody, barbaric act of terror” and said Russian authorities captured four suspects as they tried to escape through a “passage” to Ukraine. A “window” was prepared for them on the Ukrainian side of the border.

Russian media showed videos apparently showing the detention and interrogation of suspects, with one suspect telling cameras that an unidentified assistant to an Islamic preacher contacted him via a messaging app and paid to take part in the raid.

Russian news reports said the gunman was a citizen of Tajikistan, a predominantly Muslim former Soviet republic in Central Asia that borders Afghanistan. As many as 1.5 million Tajiks work in Russia, many of whom hold Russian citizenship.

Tajikistan’s foreign ministry denied initial reports in Russian media that named several other Tajiks as suspected participants in the attack, but did not immediately respond to a request for comment on the arrests.

Many Russian hard-liners have called for a crackdown on Tajik immigrants, but Putin appeared to reject the idea, saying “no force can sow poisonous seeds of discord, panic or disunity in our multi-ethnic society.”

He declared Sunday a day of mourning and said extra security measures were implemented across Russia.

The death toll was 133, making it Russia’s worst attack in years. Authorities said the death toll was still likely to rise.

The raid is a major embarrassment for the Russian leader, who comes just days after he consolidated his six-year rule over the country in a vote that It was the harshest crackdown on dissent since the Soviet era.

Some commentators on Russian social media questioned why authorities, which ruthlessly suppress any opposition activity and silence independent media, failed to prevent the attacks despite U.S. warnings.

The attack came two weeks after the U.S. Embassy in Moscow issued a notice urging Americans to avoid crowded places because of “imminent” plans by extremists to target large gatherings in Moscow, including concerts. Several other Western embassies repeated the warning. Earlier this week, Putin denounced the warning as an attempt to intimidate Russians.

Investigators were searching the charred remains of the lobby for more victims Saturday. Russia’s health ministry said hundreds of people lined up in Moscow to donate blood and plasma.

Putin claimed the attackers were trying to flee to Ukraine, following comments from Russian lawmakers in the immediate aftermath of the attack pointing the finger at Ukraine.

Ukrainian President Volodymyr Zelensky angrily dismissed Moscow’s accusations, saying Putin and his deputies were trying to shift blame onto Ukraine while treating his own people as “sacrifice.”

“They are burning down our cities – and they are trying to blame Ukraine,” he said in a statement on his messaging app channel. “They torture and rape our people and blame them. They drive hundreds of thousands of terrorists onto our Ukrainian soil to fight against us and they don’t care what happens inside their own country.”

Pictures shared by Russian state media showed emergency vehicles still gathering outside the ruins of the concert hall, which can accommodate more than 6,000 people and has hosted many large events, including the 2013 Miss Universe beauty pageant featuring Donald Trump.

Crowds gathered at the venue for a picnic concert by a Russian rock band on Friday.

Video posted online showed gunmen shooting at civilians at close range at the venue. Russian news reports cited authorities and witnesses as saying attackers threw explosive devices that started a fire that eventually burned down the building and caused its roof to collapse.

Dave Primov, who survived the attack, told The Associated Press that the gunman “shot directly into the row of people.” He described the chaos in the hall as concertgoers scrambled to escape: “People started to panic, started running and bumping into each other. Some fell, some stepped on them.”

After he and others climbed out of the lobby into a nearby utility room, he said he heard the crackle of small explosives and smelled something burning as the attackers set fire to the building. When they left the massive building 25 minutes later, it was engulfed in flames.

“If it had been any longer, we would have been trapped in the fire,” Primov said.

Messages poured in from around the world expressing outrage, shock and support for the victims and their families.

White House press secretary Karine Jean-Pierre said in a statement that the United States condemned the attack and noted that the Islamic State group was “a common terrorist enemy that must be defeated everywhere.”

The Islamic State has long targeted Russia after losing most of its ground after Russia launched military operations in Syria. In a statement carried by the group’s Amaq news agency, Islamic State’s Afghan affiliate said it attacked a large group of “Christians” in Krasnogorsk.

The group issued a new statement on Aamaq on Saturday, saying the attack was carried out by four men who used automatic rifles, pistols, knives and Molotov cocktails. The attackers allegedly fired into the crowd and killed some concertgoers with knives in an attack that was part of the Islamic State’s ongoing war against countries it claims to fight Islam.

In October 2015, a bomb planted by IS shot down a Russian passenger plane over the Sinai Peninsula, killing all 224 people on board, most of whom were Russian holidaymakers returning from Egypt.

The group operates primarily in Syria and Iraq but also operates in Afghanistan and Africa and has been responsible for a number of attacks in Russia’s restive Caucasus region and elsewhere over the past few years. It recruited fighters from Russia and other parts of the former Soviet Union.

The group’s affiliate in Afghanistan is known as ISIS-K or IS-K, named after the Khorasan province, which covered much of Afghanistan, Iran and Central Asia in the Middle Ages.

The affiliate has thousands of militants and they have carried out multiple attacks in Afghanistan since the country was occupied by the Taliban in 2021, with whom they have very tense relations.

ISIS-K was behind a suicide bombing at Kabul Airport in August 2021 that killed 13 U.S. troops and about 170 Afghans during the chaotic U.S. troop withdrawal. They also claimed responsibility for a bomb attack that killed 95 people during a commemorative march in Kerman, Iran, in January.

On March 7, just hours before the U.S. Embassy warned of an impending attack, Russia’s top security agency said it foiled an attack by the Islamic State group on a synagogue in Moscow and in Kalu, near the Russian capital. Several members of the group were killed in Canada. Days earlier, Russian authorities said six suspected Islamic State members had been killed in a shootout in Ingushetia, Russia’s Caucasus region.