Dmitry Medvedev, the former president of Russia, was quoted as warning on Monday that any intrusion on the Crimean peninsula by a NATO member-state may be considered a declaration of war against Russia and result in “World War Three.”

“Crimea is a part of Russia to us. And that indicates always. Any effort to invade Crimea is an act of war against our nation “Argumenty I Fakty, a news outlet, was informed by Medvedev.

“And if this is done by a NATO member-state, this means conflict with the entire North Atlantic alliance; a World War Three. A complete catastrophe.”

Medvedev, now deputy chairman of Russia’s Security Council, also said that if Finland and Sweden joined NATO, Russia would strengthen its borders and would be “ready for retaliatory steps,” and that could include the prospect of installing Iskander hypersonic missiles “on their threshold.”