Ukrainian officials have reported missile attacks and shelling in several regions, as Russian forces focus their efforts on the frontlines in Luhansk. But they claim further successes in the Kharkiv region.
A rare missile strike was reported in the western Lviv region.
Serhiy Hayday, head of the Luhansk regional military administration, said early Sunday that the "Russians are gathering equipment and manpower closer to Severodonetsk and preparing to attack it."
Severodonetsk is one of several industrial towns in the east that have seen relentless bombardment for weeks as Russian forces try to break down Ukrainian defenses.
Hayday said the city's chemical plant and high-rise buildings had been hit.
There is a lot of destruction: 11 high-rise buildings in the new and old districts of the city (were hit), in several of them apartments caught fire."
Several settlements to the south and west of Severodonetsk were also hit — including Vrubivka and Komyshuvakha — Hayday said.
Russian forces are expected to advance further west if they can secure Severodonetsk, where 15,000 people are still living. Most residents have been evacuated.
Ukraine has provided few details about its counter-offensive in the Kharkiv region, where its troops have made significant advances to the north and east towards the Russian border. The aim of the Ukrainian offensive is to cut Russian supply lines to its forces trying to advance into the Donetsk region.
The armed forces General Staff said Sunday only that "in the Kharkiv direction, enemy units did not conduct active hostilities."
However, Oleh Syniehubov, head of the Kharkiv regional military administration, said Ukrainian units "are constantly strengthening their positions, pushing the enemy from the borders of the city of Kharkiv to the borders of the Russian Federation. The northern and north-eastern directions are the hottest; there are active hostilities there."
He said the city of Kharkiv "has been relatively quiet for several days now, there has been no shelling of the city itself. About 2,000 people return to Kharkiv every day, and the number is growing every day."
This is partly because the city is now beyond the reach of many Russian artillery and rocket systems.
But further south, according to Syniehubov, several towns had come under fire.
He said that "the enemy is constantly checking the positions of our armed forces near Barvinkove, trying to break through but has no success. The enemy suffered heavy losses of manpower and equipment."
The General Staff also said that Russian forces were intensifying efforts in this area, reporting that "the enemy tried to break through the defenses of our troops but was unsuccessful. It continues the regrouping of troops to resume the offensive in the direction of Barvinkove and Sloviansk," two key goals for Russian forces in the region.
Elsewhere, the General Staff reported further air strikes on the Chernihiv and Sumy regions of northern Ukraine. Dmytro Zhyvytskyy, head of the Sumy region military administration, said rockets and airstrikes overnight had damaged border villages but there had been no casualties.
On the southern front, regional authorities say the Russians have begun digging trenches in some front-line positions.
The Zaporizhzhia regional military administration said the Russians "are digging trenches along the Molochna River" while continuing to shell towns in the area.
In the western Lviv region, close to the Polish border, Maksym Kozytskyi, head of the Lviv regional military administration, said "four enemy missiles hit a military infrastructure facility in the Yavoriv district, near the border with Poland. The object is completely destroyed."
Kozytskyi did not specify the target, but a previous missile attack in Yavoriv targeted training grounds where some foreign fighters were present.