Both Russian and Ukrainian forces claim to be in control of Lysychansk, the last disputed major city in the Luhansk region.
On Saturday, Chechen leader Ramzan Kadyrov published a video which purportedly shows Chechen soldiers in the city.
In the film, one of their commanders declares the city is under full control and a clean-up operation is underway.
However, Kyiv rejected the claims and said that heavy fighting is still ongoing on the fringes of the city.
A spokesman for the Ukrainian National Guard denied Lysychansk has been encircled, claiming it remains under the control of Ukraine.
Ukrainian fighters have spent weeks trying to defend the city and to keep it from falling to Russia, as neighboring Sievierodonetsk did a week ago.
“Over the last day, the occupiers opened fire from all available kinds of weapons,” Luhansk Governor Serhiy Haidai said Saturday on the Telegram messaging app.
A river separates Lysychansk from Sievierodonetsk, and Oleksiy Arestovych, an adviser to the Ukrainian president, said during an online interview late Saturday that Russian forces had managed for the first time to cross the river from the north, creating a “threatening” situation. He said they had not reached the center of the city, but control over Lysychansk would be decided by Monday.
The country's armed forces are under pressure but still fighting back. They shared footage of what they said was an explosion at a Russian army warehouse in the east of the country. The exact location and date were not specified.
Moscow meanwhile said more Russian missiles have been fired in the north and south.
The Defence Ministry claims to have used high-precision weapons to destroy five command posts in the Donbas and Mykolayev regions.
It also said three ammunition depots were hit in the vicinity of Zaporizhzhia along with a Ukrainian weapons base in Kharkiv.
The incidents took place after an apartment block was hit in Odesa killing at least 21 people and injuring dozens - an act the Ukrainian President Volodymyr Zelenskky has called 'deliberate' - a claim the Kremlin denies.