Russia is sending advanced surface-to-air missiles to the Crimean peninsula amid mounting tensions with Ukraine. The escalation comes after Russia’s Navy captured three Ukrainian ships Sunday and arrested sailors near a narrow waterway separating Russia from Crimea—which Russia seized and illegally annexed in 2014. On Tuesday, Ukrainian President Petro Poroshenko said Ukraine faces the prospect of an all-out war with Russia.

President Petro Poroshenko: “These Russian tanks were not withdrawn yet. They remain at the Ukraine-Russia border. And that’s why I don’t want anyone to think that it’s entertainment or a game. The country is under the threat of a full-fledged war with the Russian Federation.”