Thousands of Russian soldiers have been encircled by Ukrainian forces in a key occupied town in the Donetsk region, Kyiv has said.
Lyman was captured by Russia in May but has come under pressure in recent days as Ukraine's troops seek to build on gains made during ongoing counter-offensives in the north and northeast of the country.
The town has been described by analysts as strategically important to Moscow because it is home to a major rail junction which serves the western edge of the Donbas region.
The capture of Lyman could pave the way for Ukraine to make inroads into the adjacent Luhansk province, foiling Russian president Vladimir Putin's goal of seizing all of the industrial Donbas region, military experts said.
"The Russian grouping in the area of Lyman is surrounded," Serhii Cherevatyi, a spokesman for Ukraine's forces in the east, told local media on Saturday morning.
The Russian Defence Ministry did not immediately respond to a request for comment.
Fighting continued in Lyman throughout the morning. At around 11.20am a video was posted to social media purportedly showing Ukrainian soldiers raising the country's national blue and yellow flag at the entrance to the town.
In the video - posted by president Volodymyr Zelensky's head of office Andriy Yermak - two soldiers can be heard saying in Ukrainian: "[Today is] 1 October. We're unfolding our state flag and putting it on our land."
The person added: "Lyman. All will be Ukraine".
Russia has 5,000 to 5,500 troops in Lyman but their numbers may be lower because of casualties and troops trying unsuccessfully to break out, a spokesperson for Ukraine's eastern forces said.
Ukraine's military has so far not officially confirmed that Lyman has been recaptured.
The capture of the town would be a major setback for Russia after Mr Putin proclaimed the annexation of the Donetsk region, along with three others, at a ceremony in Moscow on Friday which was condemned by Kyiv and the West as a farce.
