By John Irish, Jarrett Renshaw and Andreas Rinke KANANASKIS, Alberta (Reuters) -Group of Seven leaders faced early challenges during meetings in Canada on Monday as U.S. President Donald Trump said removing Russia from the former Group of Eight over a decade ago had been a mistake.

A mass drone attack struck several districts of the Ukrainian capital Kyiv early on Tuesday, damaging an apartment building and injuring up to 11 people, city officials said. Mayor Vitali Klitschko said swarms of drones continued to move towards the capital and warned of a danger of Russian missiles being deployed.

Families in Ukrainian cities are taking refuge from massive swarms of Russian drones, as Moscow steps up its airborne assault with attacks designed to undermine Ukrainian morale.

Ukraine alleged Monday that Russia mixed bodies of its own dead soldiers among the Ukrainian military dead that have been returned, and that more than a million Russians have been killed since conflict began.

Ukraine and Russia have completed an exchange of dead bodies - the final stage of a deal to bring home fallen soldiers. Kyiv said Moscow handed over 1,245 bodies on Monday, bringing the total to 6,057 in the past few days. It said it was now verifying whether all the bodies were indeed of Ukrainian soldiers.

Ukraine received another 1,245 bodies of its soldiers killed in the war with Russia on Monday in the final stage of the repatriation of remains agreed at talks in Istanbul, Ukrainian officials said. "Today marks the final stage of the repatriation of fallen soldiers,