VLADIMIR Putin has threatened to step up nuclear strikes against countries that “interfere” with Russia’s invasion of Ukraine. The Russian leader issued a warning in a speech in St Petersburg, and threatened ‘lightning fast’ retaliatory strikes against the besieged country’s allies. Putin warned: “If someone from the outside tries to intervene in Ukraine then our response will be lightning-fast,” he said. “We have all the weapons we need for this. No one else can brag about weapons, and we won’t brag about them. But we will use them.” It comes after Russia yesterday threatened to smash Britain with its terrifying 16,000mph “Satan 2” nuke for supplying military hardware to Ukraine. The terrifying RS-28 Sarmat missile is capable of holding 15 warheads and travelling a distance of more than 11,000 miles – with the potential to obliterate an area the size of the UK in a single strike. And in a chilling warning, pro-Putin TV anchor Vladimir Solovyov threatened to blow Britain to smithereens using the terrifying projectile. “As it turned out, one Sarmat means minus one Great Britain,” he said. Follow our Russia-Ukraine live blog below for up-to-the-minute updates…