Ukraine cities face intense shelling as Russian convoy closes in on Kyiv

Ukraine's embattled leader accused Russia of war crimes and "state terrorism" Tuesday after a fresh blast struck the heart of the country's second-largest city, fueling fears civilians would face the brunt of an intensifying assault.

As the conflict escalated on its sixth day, Russia hit major cities across Ukraine with increasingly heavy shelling while a vast convoy of its forces threatened the capital.

Ukrainian President Volodymyr Zelenskyy vowed to defend Kyiv and sought to rally both his country and the international community against what he called "outright, undisguised terror" from Moscow, in a video message posted on social media.

Global condemnation and crippling sanctions have left the Kremlin isolated in the wake of last week's invasion, confronting a spiraling economy and dogged defense from Ukrainian forces. U.S. officials said they feared Russian President Vladimir Putin, frustrated by his military's struggles, may see greater violence as his only option.

Facing fierce resistance on the ground, Moscow appeared to ramp up its assault from the air, which Ukraine and international watchdogs said was increasingly hitting civilians.