As Russia comes to terms with what seems to be the largest terrorist attack on its soil in recent times, Vladimir Putin has something difficult to explain. For some time, Western intelligence agencies have been picking up chat about potential strikes in Moscow – and the US took the unusual step of making a public warning. ‘The Embassy is monitoring reports that extremists have imminent plans to target large gatherings in Moscow, to include concerts, and US citizens should be advised to avoid large gatherings over the next 48 hours,’ ran the advice.

Just three days ago, as reported by the Russian state media agency TASS, Putin branded these warnings ‘outright blackmail’ whose intention was ‘to intimidate and destabilise our society’. The warning – and his dismissal – is being highlighted by opposition Telegram channels and set against the carnage that Russia is confronted with this evening.

This incident is the largest terrorist attack to happen on Russian soil in recent times

Nothing is known about the motives or identity of the gunmen who opened fire at a music venue on the outskirts of Moscow just after 8pm local time. At the time of writing, as many as 40 people have reportedly been killed and 130 wounded at the Crocus City Hall music venue in the suburb of Krasnogorsk, 15 miles from Moscow’s city centre. They struck as hundreds people were arriving to hear the rock band Picnic perform. Footage circulating on social media reportedly taken by concert-goers hiding on the upper levels of the venue’s lobby shows at least two men entering the building in combat fatigues and opening fire with machine guns as they progress further inside. The venue’s security guards, seen in the background of the footage, appear to be lying dead or injured on the floor.

Further videos seemingly taken by those who had already made their way into the concert hall show Russians screaming and dropping to the floor as the sounds of shots echo loudly through the building. Emergency services, including approximately 50 ambulances, and police managed to reach the scene and evacuate as many people as possible. Nevertheless, reports suggest that people remain inside the building. Soldiers from the Rosgvardia, Russia’s national guard, have also since been dispatched to the scene.

During the incident, the venue’s roof caught fire and has reportedly since collapsed. Footage taken by eye witnesses, also since circulating on social media, show huge plumes of flame engulfing the entire roof.

With the situation still ongoing, many details are currently difficult to confirm. It is unclear how many gunmen actually were at the scene: the reported number ranges between two and five. What their motive was is also currently unknown. What or who caused the roof to catch fire will also take time to determine; some eye-witness reports have suggested it could have been caused by a grenade or bomb thrown by one of the attackers or seats that had been set fired to. A reported 3,000 square metres of the building has now been destroyed by flames.

This looks very much like the kind of attack that the US government was warning about – and Putin publicly dismissed. As the recent presidential election demonstrated, there is not much in the way of official opposition: difficult questions are posed by expats and anonymous critics. But as Muscovites recoil from this atrocity, it seems that Putin does have questions to answer.