A terrorist attack could target Moscow in the next 24 hours, the British and American embassies in Russia have warned. Last night’s ‘security alert’ from the US embassy said it was “monitoring reports that extremists have imminent plans to target large gatherings in Moscow, to include concerts”. The statement also said American citizens “should be advised to avoid large gatherings over the next 48 hours”. It told US citizens in Moscow to “avoid crowds”, “monitor local media for updates” and “be aware of [their] surroundings”. The warning was repeated by the UK, which continues to advise agains…