MOSCOW—Russian President Vladimir Putin has signed a decree suspending Russia's participation in a key European arms control treaty, the Kremlin said Saturday. The Kremlin said in a statement the need to pull out of Conventional Forces in Europe Treaty was linked to "extraordinary circumstances ... which affect the security of the Russian Federation and require immediate measures." The treaty is seen as a key element in maintaining stability in Europe. It establishes limitations on countries' deployment of tanks, armored combat vehicles, artillery, attack helicopters and combat aircraft.