Ukrainian officials have acknowledged the loss of several communities near the city of Lysychansk, the only conurbation in Luhansk region they still control.
"The Russians are approaching Lysychansk, entrenching in nearby towns. The city is being shelled by aircraft," said Serhiy Hayday, head of the Luhansk regional military administration.
Hayday said it was "difficult" in the area south of Lysychansk. "The enemy entered Toshkivka, which allowed it to increase fire on other settlements."
Russian forces were entrenched in several villages immediately to the south of Lysychansk, including Ustynivka, Pidlisne and Myrna Dolyna, and were advancing at Bila Hora.
"It is not easy for our soldiers to keep the defense," Hayday said
His comments suggest that Ukrainian defenses around Lysychansk have begun to succumb to much greater Russian firepower, after weeks of bombardment.
Hayday said "street fights continue in Severodonetsk," where Ukrainian defenders still occupy a part of the Azot chemical plant.
But he said the Russians were trying to surround Ukrainian units in some localities (such as Borivske) near Lysychansk and Severodonetsk. Military analysts have said the risk of a Russian advance from the south is that some Ukrainian troops could be cut off.
"Lysychansk is under heavy fire now. The city is shelled from artillery, tanks and aircraft. There are at least three wounded civilians there, several policemen were injured," Hayday said. Police and security service buildings were also hit by missiles.
Some context: Throughout its campaign, Russia has used the tactic of intense bombardment before trying to take territory.