The refusal of Ukraine and Western powers to recognize Moscow’s control of Crimea poses a “systemic threat” to Russia and any external attack in the region will trigger a “Doomsday” response, former president Dmitry Medvedev said on Sunday. Russia annexed the Black Sea peninsula of Crimea from Ukraine in 2014 after a pro-Moscow president was ousted in Kyiv amid mass street protests. Subsequently, Moscow also supported pro-Russian armed separatists in the Donbass region of eastern Ukraine. In the event of an attack on Crimea, Medvedev, according to the TASS news agency, said: “The Day of Judgment will come very quickly and hard. It will be very difficult to hide.” Medvedev did not elaborate, but has previously warned the United States about the dangers of trying to punish a nuclear power like Russia for its actions in Ukraine, saying it could endanger humanity. His comments came a day after a Ukrainian official suggested that Crimea, which most of the world still recognizes as part of Ukraine, could be a target for US-made HIMARS missiles newly deployed by Kyiv as it battles Russian forces. Earlier on Sunday, the Interfax news agency quoted Medvedev as telling World War II veterans: “If any other state, be it Ukraine or NATO countries, believes that Crimea is not Russian, then this is a systemic threat to us.” “This is a direct and explicit threat, especially given what had happened in Crimea. Crimea has returned to Russia,” said Medvedev, who now serves as the vice chairman of Russia’s Security Council. Vadym Skibitskyi, an official in Ukraine’s military intelligence service, was asked on Saturday in a televised interview whether HIMARS could be used on targets in Crimea. He said Russia had carried out strikes on Ukrainian soil from Crimea and the Black Sea, so those were also legitimate targets. Crimea is of particular strategic importance to Russia as it includes the headquarters of its Black Sea fleet in Sevastopol. The Morning Update and Afternoon Update newsletters are written by Globe editors, giving you a concise summary of the day’s most important headlines. Sign up today.