Even as Islamic State says that it was behind the Moscow massacre, Putin cynically points the finger at Kyiv

Russian leader Vladimir Putin last night accused Ukraine of assisting the terrorists behind an attack on a Moscow theatre that left at least 133 dead – despite Islamic State claiming responsibility for the atrocity.

Four gunmen armed with automatic weapons and bombs launched a killing spree inside the Crocus City Hall theatre on Friday night. It is the worst terrorist attack in Russia for 20 years.

The massacre came two weeks after the US warned of an imminent attack in the Russian capital by extremists.

Within hours, Islamic State had issued a statement saying that it was behind the attacks and posted a picture of the gunmen on its social media channel. But in an angry national address yesterday, Putin pointed the finger at Ukraine.

The Russian leader claimed that the terrorists had fled the scene in a white Renault and travelled 248 miles south to the Bryansk region, where they were about to cross the border into Ukraine.

Russian president Vladimir Putin accused Ukraine of assisting the terrorists behind the attack on the Crocus City Hall in Moscow last night

Pictured: One of the men detained who is accused of being involved in the attack

Rescuers working inside the Crocus City Hall a day after terrorists opened fire on crowds

The smouldering remains of the concert hall venue can be seen here a day after the horrific attack

A view shows the burning Crocus City Hall concert hall following the shooting incident in Krasnogorsk, outside Moscow 

A massive blaze is seen over the Crocus City Hall in the western suburbs of Moscow, 12 miles from the Kremlin

A picture from the scene last night shows the Crocus City Hall concert hall engulfed in flames as the venue is surrounded by emergency service crews

A video grab showing people evacuating the Crocus City Hall in the Russian capital, which was hosting a sold out concert by rock band Piknik

He said: 'They tried to hide and moved towards Ukraine, where, according to preliminary data, a window was prepared for them on the Ukrainian side to cross the state border.'

Eleven people had been arrested, he added, including the four terrorists: 'The Russian Federal Security Service and other law enforcement agencies are working to identify and uncover the entire auxiliary base of the terrorists.

'Those who provided them with transport, plotted ways of getting away from the scene of the crime, prepared caches and hiding places with weapons and ammunition.'

But a spokesman for Ukraine's President Volodymyr Zelensky angrily denied any involvement in the attacks, saying: 'Ukraine has never resorted to the use of terrorist methods. Everything in this war will be decided only on the battlefield.'

Last night, US officials said that the claim of responsibility by Islamic State was credible, adding that Islamic State Khorasan Province, which is based in Afghanistan, may have carried out the attack.

The US had intelligence of an imminent assault by 'extremists' earlier this month, and issued a warning to its citizens in Moscow to avoid large public gatherings.

The Crocus City Hall theatre, which lies 12 miles from the Kremlin in the north-west of the city, has a capacity of 6,200.

Friday night's concert – by Piknik, a Soviet-era rock band – was said to be sold out.

The massacre began at 7.40pm local time as concert-goers were filing into the auditorium.

Witnesses said at least four gunmen, in camouflage and combat vests with dozens of spare magazines, leapt out of a white Renault minivan and headed calmly towards the metal detectors at the theatre's entrance. There they shot through the glass doors and windows, killing dozens.

The terrorists were then captured on grainy mobile-phone footage, shooting as they walked through the concert hall's foyer.

'They acted like trained fighters,' one witness said. 'They killed the guards and people standing at the door. Then they blocked the main entrance.'

Graphic footage showed the gunmen firing on those trapped in an entrance for a full minute at point-blank range.

Image of the suspected gunmen who opened fire at Crocus City Hall, in Krasnogorsk, Moscow

A map showing the location of the Crocus City Hall, which is situated 12 miles from the Kremlin in central Moscow

After that, the attackers lobbed an explosive device into the crowd, starting a fire which eventually burnt through the venue's roof.

One woman, in hospital being treated for burns to her hands and body, told Russian TV: 'I fell to the floor and pretended to die. The girl next to me was killed.'

Yulia Khvatkova, who saw the carnage at the entrance, said: 'I was wounded in the shoulder, my boyfriend was hit in the arms and legs. A woman fell right next to me with a bullet through her temple.

'A cheerful woman was selling tickets at the entrance. When we ran away I saw her lying there with these tickets with a bullet in her head.'

The musicians were still in their dressing room when gunshots first rang out. At first, the audience inside the auditorium thought it was part of the build-up to the show. Then, when it became clear an attack was under way, loudspeakers blared out that the concert was being cancelled for 'technical reasons'. There was panic as trapped concert-goers tried to flee.

Yesterday, emergency workers could be seen searching through the wreckage of the theatre, looking for bodies and survivors. They reportedly found 28 bodies in a toilet and 14 on an evacuation staircase.

Victims were found lying dead in family groups, some embracing their loved ones. Reports said several children were among the victims. Around 140 have been injured, with half still in hospital.

The gunmen were captured six hours later by Chechen fighters loyal to Putin in the Bryansk region. All four men detained are believed to be Muslims from Tajikistan, which borders Afghanistan.

In footage released on social media, one of the captured terrorists said he had been ordered to attack the theatre for a million roubles (£8,599).

It is the worst terrorist attack in Russia since the 2004 Beslan school massacre, where 334 victims were killed, half of whom were children.

In 2002, a siege of the Dubrovka Theatre in Moscow by Chechen terrorists left 132 hostages dead.