Russian forces, even as they scramble to respond to a surprise incursion from northern Ukraine into Russia last week, are continuing to pummel Ukrainian forces along the front lines in eastern Ukraine, Ukrainian military officials said Monday.

“Our guys do not feel any relief,” said Artem Dzhepko, a press officer with Ukraine’s National Police Brigade, which is fighting near the strategically important town of Chasiv Yar in the Donetsk region of eastern Ukraine.

He said Russian forces were continuing to use aerial bombs, as many as 10 a day, against Ukrainian positions. Mr. Dzhepko added: “It’s hard. Unfortunately, the pressure of the Russians did not decrease.”

At the same time, Ukrainian troops have been pushing to the northwest and west in Russian territory, according to a briefing Sunday from the Institute for the Study of War, a U.S.-based think tank.

Several thousand Ukrainian troops crossed into Russia on Aug. 6, a new front in the third year of the war and the first time the Ukrainian army has made such an extensive foray into Russia, military analysts say.

Instead of pulling brigades from the front lines in eastern Ukraine to help stop the incursion into Kursk, the region along Russia’s southwest border with Ukraine, Russia appeared to be redeploying lower-level units to the Kursk region, according to the Institute for the Study of War’s briefing.