Snowflakes cover the photograph of a fallen Ukrainian service member March 12, 2024, in downtown Kyiv, Ukraine. An elderly Ukrainian woman eats a slice of bread inside a crowded Lviv railway station Feb. 28, 2022, in Lviv, west Ukraine.

Ukrainian troops have launched an attack against a Russian border region with six US long-range missiles, Moscow has said. It comes after Vladimir Putin approved an updated doctrine lowering the threshold for the use of nuclear weapons.