Ukraine's acting president says its military is "on full combat alert" against a possible invasion by Russian troops massed on the border.
Across the globe, people flocked the streets on May 1 to celebrate International Labor Day, or May Day.
A strong storm system moving across the central and southern United States has spawned several tornadoes, killing at least 16 people in an outbreak forecasters say could continue as the storms continue traveling to the east.
Pro-Russian activists storm an administration building in the center of Luhansk, Ukraine, further raising tensions in the east, where insurgents have seized control of police stations and other government buildings in at least 10 cities and towns.
Two bombs have exploded in Iraq, killing at least 10 people a day before the country holds it first national elections since the withdrawal of U.S. troops in 2011.