Ukrainians mark 31 years since they broke free from the Russia-dominated Soviet Union on Wednesday in what is certain to be a day of defiance against the Kremlin's six-month-old war to subdue the country once again.

Ukraine's Independence Day falls six months after Russia's Feb. 24 invasion and will be observed with subdued celebrations under the threat of attack from land, air and sea.

Public gatherings are banned in the capital Kyiv and a curfew is in force in the front-line eastern city of Kharkiv, which has weathered months of shelling.