It was a warning that proved grimly prophetic. Just over two weeks ago, as Russia’s presidential election was reaching its final stages, the US embassy in Moscow said it was “monitoring reports that extremists have imminent plans to target large gatherings in Moscow, to include concerts” over the ensuing 48 hours. The unusually clear public alert was repeated by the UK, which reiterated its longstanding advice, warning British citizens against going to Russia. As a close ally in the Five Eyes intelligence alliance, Britain will have seen whatever raw intelligence the US warning was based on, most likely intercepted communications. No attack came within that timeframe, but it is now tragically clear the respite was only temporary. A terrorist attack on Friday night by a group of gunmen on crowds attending a pop concert on the outskirts of Moscow has left at least 133 dead and 140 wounded, responsibility for which was claimed by Islamic State. Whether more details underpinning the warning were passed from the US to their Russian counterparts is unclear, given the two countries are engaged in a proxy war in Ukraine, nor is it certain the alert would have been well received. But it is an uncomfortable reminder that large-scale terror attacks have not gone away. Moscow, meanwhile, is trying to promote an alternative theory. The Russian president, Vladimir Putin, sought to accuse Ukraine of involvement, saying that the four suspects now apprehended had “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”. Given Russia’s war in Ukraine, the claim is unsurprising. But on any initial assessment it lacks credibility. While Ukraine has been seeking to strike military and industrial targets hundreds of miles inside Russia, its leaders well understand they would rapidly forfeit international support if they carried out a massacre of civilians. Ukraine has targeted airbases and seaports inside Russia, and it may even have flown two drones over the Kremlin. This year Kyiv almost certainly attacked a gas terminal in St Petersburg and refineries in Yaroslavl and Volgograd, escalation enough to prompt anxiety in the US, worried about the impact on global oil prices. But none of these are mass casualty attacks aimed at peacefully congregating civilians. Even if those apprehended by Moscow prove to be the gunmen and were heading south, it would not be obvious their best strategy would be to cross the frontlines of an active war. “Everything in this war will be decided only on the battlefield,” said Mykhailo Podolyak, a senior adviser to Ukraine’s president, Volodymyr Zelenskiy, on Friday night, adding: “Terrorist attacks do not solve any problems …” Moscow may appear far away from the west, but it is also far from Kerman, Iran, the site of a terror attack in January claimed by Islamic State Khorasan Province (ISKP) that killed 84. If it is confirmed that the Moscow attack was carried out by the same group, it is uncomfortable reminder that it is on the rise. ISKP was also behind another suicide bomb attack at Kabul airport, Afghanistan, in August 2021, killing 170 Afghans and 13 US troops, in the process of carrying out the retreat from the country ordered by the US president, Joe Biden, a few months earlier. Its focus may have been Russia on Friday, but it was US forces less than three years ago. The mass killing at a concert venue also carries with it obvious chilling echoes of the murderous attack, also by IS gunmen, at the Bataclan in Paris in November 2015, which killed 89, and the suicide bombing at the Manchester Arena in 2017 after an Ariana Grande concert, which killed 22. Last year, leaks from US intelligence showed that ISKP, based in Afghanistan, was conducting “aspirational plotting” in the US, Europe and Asia, with targets such as the last World Cup in Qatar in mind. Whatever the west’s wider relationship with Moscow is, counter-terror investigators know it is time to be particularly vigilant.