Former heavyweight champion Vitali Klitschko, the mayor of Ukraine's capital of Kyiv, said he and his brother Wladimir will take up arms to defend against Russia's invasion.
Explosions sounded before dawn in Kyiv as Western leaders scheduled an emergency meeting and Ukraine's president pleaded for international help to fend off an attack that could topple his democratically elected government, cause massive casualties and ripple out damage to the global economy.
The nature of the explosions was not immediately clear, but the blasts came amid signs that the capital and largest Ukrainian city was increasingly threatened following a day of fighting that left more than 100 Ukrainians dead.
Mayor Vitali Klitschko tweeted that three people were injured, one was in critical condition, after missile debris hit a residential building.
He also posted a photo showing a building with part of its wall torn down and emergency services present at the scene.
Russia pressed its invasion of Ukraine to the outskirts of the capital Friday after unleashing airstrikes on cities and military bases and sending in troops and tanks from three sides in an attack that could rewrite the global post-Cold War security order.
On Thursday, Russian President Vladimir Putin authorised "a special military operation" in Donbas, and Ukraine confirmed that military installations across the country were under attack.
Ukrainian airfields, command posts, naval bases and radar stations were among the facilities destroyed, according to the Russian Defence Ministry.
