Russia's ballistic missile attack on Ukraine’s capital, Kyiv, killed at least one person; a Ukrainian attack on Russian border town killed six, officials say.

Igor Kirillov, who was named the head of Russia’s nuclear defense forces in April 2017, was under sanctions from several countries including the U.K. and Canada for his role in Ukraine.

Ukraine’s capital faced a Russian missile attack for the first time in almost a month, a day after Kremlin leader Vladimir Putin offered to hold talks with US President-elect Donald Trump.

Ukraine’s Security Service, or SBU, has claimed responsibility for killing Lt. General Igor Kirillov, head of the military’s nuclear, biological and chemical protection forces, in a bombing Tuesday in Moscow.

Moscow said its attack on Ukraine was in retaliation for a strike by Western missiles on a chemical plant in Russia earlier in the week. Russia says it has seized two more Ukrainian settlements Russian forces have taken control of two more settlements in Ukraine's eastern Donetsk region,