President Volodymyr Zelensky made a dramatic visit to the newly recaptured Izium on Wednesday, raising the Ukrainian flag over the strategic city and underscoring the failure of Russia’s campaign in the northeast.

Zelensky, standing in a cold drizzle amid wreckage left behind by the fleeing Russian Army, told soldiers assembled before him in front of the bombed-out municipal building: “Our blue-and-yellow flag is already flying in de-occupied Izium. And it will be so in every Ukrainian city and village.”

Zelensky’s visit came as Ukrainian forces continued to sweep south from the Kharkiv region, and were fighting on the outskirts of Lyman, a city at the doorstep of the Luhansk region.

Russia captured Luhansk over the summer in a monthslong campaign that razed cities and left thousands of soldiers on both sides dead.

With Ukraine having captured the momentum on the battlefield in the nearly seven-month-old war, President Vladimir V. Putin of Russia is confronting more vocal criticism over his faltering invasion.

At a meeting of Russia’s parliament on Tuesday, the leader of the Communist Party, Gennady Zyuganov, joined those calling for Moscow to announce a full military mobilisation, which Putin has declined to do in order to preserve the sense at home that his “special military operation” is limited and proceeding according to plan.

“A special operation is something you announce — and something you can choose to put an end to,” Zyuganov said, according to Meduza, an independent Russian news site.