A group of Isis gunmen have opened fire at audience members in a concert hall near Moscow just weeks after the UK and US warned Russia faces an impending terrorist attack.
The attack has been attributed to Isis, with a security source confirming the terrorist plot to Amaq News Agency.
"Islamic State fighters attacked a large gathering of Christians in the city of Krasnogorsk on the outskirts of the Russian capital, Moscow, killing and wounding hundreds and causing great destruction to the place before they withdrew to their bases safely," a security source said.
The death toll has risen in recent hours, with the latest estimates standing at 115.
Armed gunmen open fire in Moscow concert hall just weeks after impending attack warningREUTERS/XMore than 140 people sustained injuries and the Kremlin arrested 11 jihadists, including four suspected gunmen.
Moscow has been facing an increasing number of threats from Isis in recent weeks.
The Kremlin foiled a plot to attack a synagogue in Moscow and later claimed it killed six operatives in the North Caucasus region.
The British Embassy in Moscow echoed concerns about the attack, saying: "We are aware of reports of a terrorist incident around the Crocus concert hall in Krasnogorsk near Moscow.
"British nationals should avoid the area and follow instructions of local authorities."
State news agency TASS Russia's Federal Security Service (FSB) claimed around 100 people sustained injuries at Crocus City Hall.
The venue also witnessed two explosions, Russian news agencies have claimed.
Three camouflage-clad gunmen reportedly entered the venue and soon opened fire ahead of 6,200 attending a Russian rock concert.
Telegram channel Baza shared a video showing flames and a huge plume of smoke rising from what was said to be the concert venue.
As many as 100 people were also rescued from the basement of the concert hall, emergency officials at the venue have claimed.
In a statement, FSB said: "All possible measures are being taken to provide assistance to those affected as a result of the terrorist attack in the Crocus City Hall.
"The special services are carrying out active search measures following the emergency in the Crocus complex."
Russian news agencies later revealed people were still stuck on the roof of the building.
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Smoke from fire rises above the burning Crocus City Hall concert venue following a shooting incident, outside Moscow
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Moscow Mayor Sergei Sobyanin said: "A terrible tragedy occurred in the shopping centre Crocus City today."
He added: "I am sorry for the loved ones of the victims."
White House national security adviser John Kirby said he could not yet speak about all the details but that "the images are just horrible. And just hard to watch".
He added: "Our thoughts are going to be with the victims of this terrible, terrible shooting attack.
"There are some moms and dads and brothers and sisters and sons and daughters who haven't gotten the news yet. This is going to be a tough day."
The incident took place just days after Russian President Vladimir Putin secured a fifth term in the Kremlin with yet another landslide victory.
Russia's President Vladimir Putin, accompanied by Moscow Mayor Sergei Sobyanin
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Russian Foreign Ministry spokeswoman Maria Zakharova responded: "On what basis do officials in Washington draw any conclusions in the midst of a tragedy about someone's innocence?"
London and Washington warned Moscow could face a terror attack earlier this month.
The US Embassy in Russia warned that "extremists" had imminent plans for an attack in Moscow.
The UK Embassy also posted about the situation, warning: "Extremists have imminent plans to target large gatherings in Moscow, to include concerts."
Mykhailo Podolyak, an aide to Ukrainian leader Volodymyr Zelensky, claimed Kyiv was not behind the attack.
"Let's be clear, Ukraine absolutely has nothing to do with these events," he said.
However, Russia has claimed the Isis terrorists were pursuing a Ukrainian link.