Ukraine's military warned the public on Tuesday of more indiscriminate Russian shelling from bogged-down Russian troops, and U.S. President Joe Biden issued his strongest warning yet that Russia is considering using chemical weapons.

Amid the devastation caused by Russia's unceasing bombardment of Ukrainian cities, Ukrainian President Volodymyr Zelenskyy highlighted the death of a 96-year-old survivor of Nazi concentration camps, killed in his flat by shelling in Kharkiv.

Nearly four weeks into their invasion, Russian troops have failed to capture any major Ukrainian city and have been halted on nearly all fronts, but are hammering residential districts with artillery, missiles and air strikes.