Ukrainian forces have advanced around Bakhmut, Deputy Defence Minister Hanna Maliar has said, describing the eastern city as the “epicentre of hostilities”.
She did not say whether a long awaited counter-offensive had begun.
Separately, Russia’s military said it had repelled a new attack in the eastern Donetsk region on Monday.
Bakhmut has for months been at the heart of fierce fighting. It has little strategic value – but is important symbolically both for Kyiv and Moscow.
Monday’s claims by Ukraine and Russia have not been independently verified.
In the early hours of Tuesday, air raid sirens were activated for several hours all over Ukraine. In the capital Kyiv, all missiles – more than 20 – were shot down, city officials said citing preliminary information.
In a post on social media on Monday, Ms Maliar said that “despite stiff resistance and the enemy’s attempts to hold the their positions, our military units advanced in several directions during the fighting”.
She said in Orikhovo-Vasulivka and Paraskoviivka, Ukrainian troops gained from 200m to 1,600m (656-5,250ft), while in Ivanivske and Klishchiivka they advanced between 100m and 700m (330-2,300).
All four villages are located within several kilometres of Bakhmut. The battle for the city in the Donetsk region has been the longest and bloodiest of the war.
In a video address late on Monday, President Volodymyr Zelensky thanked Ukrainian fighters for delivering “the news we are expecting” on the Bakhmut direction.
“The enemy knows that Ukraine will win,” he said.
The Russian paramilitary group Wagner had claimed to have captured the city in late May. In recent weeks, some analysts have suggested Kyiv’s forces are attempting to encircle Bakhmut and trap Russian units.