Ukraine Says It Is Engaged in Fierce Fighting With Russia in Northeast

• Mapping Russia’s Offensive
• Photos
• A Crack in Ukraine’s Line
• Using Frozen Russian Assets
• Ukraine’s Air Defenses

After surging across the border last week, Russia’s army appears to be advancing more slowly in northeastern Ukraine, Ukrainian officials and military analysts said on Wednesday, with the two sides engaged in fierce combat around villages about five miles from the border.

In a sign of the concern that Russia’s northeastern offensive is causing in Kyiv, President Volodymyr Zelensky of Ukraine canceled his participation in all international events for the coming days, including a visit on Friday to Spain where he was expected to sign a security agreement.

Civilians continued to flee areas of northeastern Ukraine under heavy shelling by Russian forces, the Ukrainian officials said, warning that their troops had to contain relentless assaults and that the situation on the ground could change fast.

Gen. Kyrylo Budanov, the head of Ukraine’s military intelligence agency, told Ukrainian television on Tuesday that conditions in the area under attack were moving “toward stabilization,” with additional Ukrainian units being rushed in to repel Russian advances. But he added that “the situation is quite tense and is changing very quickly.”

Ukraine’s General Staff said around midday Wednesday that Russian forces had “not carried out active operations since the beginning of the day” in the northeast. But it acknowledged a few hours earlier that Ukrainian troops had withdrawn from positions near two villages to avoid further casualties, allowing Russian forces to move in.

The assessments by the Ukrainian officials and analysts appeared to be supported by open-source maps of the battlefield compiled by independent groups analyzing combat footage. Those maps showed that Russian troops had gained a foothold in two settlements in the past day, a slower rate of advance than before, when they were capturing up to five settlements a day.