The death toll from a Russian rocket attack as Ukraine observed its Independence Day has risen to 25, including an 11-year-old boy found under the rubble of a house and a six-year-old killed in a car fire near a train station that was the target, a Ukrainian official said Thursday.

Russia's Defence Ministry said its forces used an Iskander missile to strike a military train that was carrying Ukrainian troops and equipment to the front line in eastern Ukraine. The ministry claimed more than 200 reservists "were destroyed on their way to the combat zone."

The deputy head of the Ukrainian presidential office, Kyrylo Tymoshenko, did not say if the 25 victims he reported from Wednesday's attack were all civilians. A total of 31 people sustained injuries, he said.

In Geneva on Thursday, UN human rights chief Michelle Bachelet decried the period since Russian President Vladimir Putin sent troops into the neighbouring country as "unimaginably horrifying." She called on Putin "to halt armed attacks against Ukraine."The lethal strike in Chaplyne, a town of about 3,500 residents in the central Dnipropetrovsk region, nonetheless served as a painful reminder that Russia's military force is causing civilians to suffer and testing Ukraine's resilience after six months of a grinding war