At least 133 people have died in the Friday Moscow concert hall massacre, the most deadly terrorist attack Russia has seen in years AP

Armed assailants on Friday stormed a concert hall in Russia's Moscow, killing 133 people and injuring dozens others

The attack came just days after Putin tightened his grip on power after winning the elections as country's war in Ukraine dragged into a third year AP

While the Islamic State group has claimed responsibility for the attack, Russia President Vladimir Putin on Saturday said the arrested suspects were "headed to Ukraine" AP

The Islamic State group's Afghanistan branch claimed responsibility for Friday's attack in a statement posted on affiliated channels on social media AP

Russian news reports cited authorities and witnesses saying that the attackers threw explosive devices that started the fire AP

The roof of the theater, where crowds had gathered for a performance by the Russian rock band Picnic, collapsed early Saturday as firefighters spent hours fighting the blaze AP

The Islamic State (IS) group, an offshoot of al-Qaida that took over much of Iraq and Syria in 2014, claimed responsibility on the social media channels AP

The US Embassy in Moscow had issued a security alert to US citizens on March 7 saying it was monitoring reports that extremists had “imminent plans to target large gatherings" in Moscow AP