Ukrainian forces are encircling Russian troops in the area of the eastern stronghold of Lyman, and have all the logistics routes into the area under fire control, a military spokesperson told the Suspilne public broadcaster on Friday.
The comments, if confirmed, suggest Russia is on the cusp of a new setback in its military campaign in the Donbas region as President Vladimir Putin prepares to declare the region part of Russia.
"All the approaches and logistic routes of the enemy, through which they delivered ammunition and manpower, are in fact under fire control (of Ukraine)," Serhii Cherevatyi, a spokesperson for eastern Ukrainian forces was quoted as saying.
Fighting was still raging, he said.
"We cannot precisely name the details of the captured places yet. Since (soldiers) may carry in and hoist the flag, they are sharing happy videos, but the fighting is continuing," he said.
Lyman has served for months as a logistics and transport hub anchoring Russian military operations in the north of Donetsk province. Its capture would be Kyiv's biggest gain since a lightning counter-offensive retook swathes of Kharkiv region this month.
The window is narrowing for Ukraine to make major advances before winter sets in, slowing operations and giving Russia, which has declared a partial mobilisation, more time to fortify its lines.
(Reporting by Tom Balmforth; editing by Timothy Heritage)