At G20 summit, U.S. and Europe blast Russia over Ukraine

U.S. President Barack Obama said on Saturday that Russia's aggression against Ukraine was "appalling" and a threat to the world, while European nations threatened further sanctions against Moscow if it did not end the flow of weapons and troops.

Speaking on the sidelines of the G20 summit in Brisbane, Obama placed security and climate change at the center stage of the leaders meeting, overshadowing talks on global economic growth.