Civilians in Lysychansk have been urged to leave immediately, as Russian forces gain ground in the last remaining city Ukraine holds in the eastern Luhansk region.
"Due to the real threat to life and health, we call for an evacuation immediately. The situation in the city is very difficult," Serhiy Hayday, the head of the Luhansk regional military administration, said on Telegram.
He promised civilians they would be taken care of in other Ukrainian cities.
Videos from Lysychansk suggest that some civilians are reluctant to leave their homes, regardless of who controls the city.
There are about 10,000 to 15,000 people still in Lysychansk, with only around 50 people leaving each day, according to Shybiko Valerii, the head of the Ukrainian Lysychansk Military Administration.
Forces from the self-proclaimed Luhansk People's Republic (LPR), which is fighting alongside the Russian military, said Monday they are developing "a successful offensive in the area of Lysychansk with the fire support of the Russian army."
"The enemy suffered heavy losses in manpower and armored vehicles," it said on its Telegram channel.
"The people's militia continues to liberate territory occupied by Kyiv," the LPR added, claiming that the village of Borivske, within 5 kilometers (3 miles) of Lysychansk, is now under its control.
Officers of the LPR militia claimed they had cut off two evacuation routes for Ukrainian troops from Lysychansk, according to a reporter from the Ria Novosti state-owned news agency.
There has been heavy fighting south-west of Lysychansk around Vovchoyarivka, close to the main highway leading west as Russian forces aim to complete the city's encirclement.