A decree signed by the Russian leader, though long planned, came days after President Biden authorized the use of U.S.-supplied missiles by Ukraine for strikes inside Russia.

Russian President Vladimir Putin conducts an exercise of Russia's strategic nuclear deterrence forces to train actions of officials on operating nuclear weapons with practical launches of ballistic and cruise missiles,

Russian President Vladimir Putin has approved changes formally lowering the threshold at which his country can consider a nuclear attack.

Markets shook off their concerns Tuesday as tensions mounted between Russia and the United States. All three major indexes were almost flat mid-afternoon after a volatile start to the day. The Dow dropped about 450 points shortly after the opening bell but swiftly rebounded.

Stock markets fell in Europe but finished mostly higher in New York Tuesday as markets weighed worries about escalating conflict between Russia and Ukraine.