Russia said Sunday that Ukraine had launched a “counterattack” in the western border region of Kursk, where Kyiv’s forces began a shock ground offensive last August.

It was not immediately clear how much Ukraine had advanced in the region, but pro-Kremlin military bloggers reported earlier that a powerful new offensive was under way.

The assault comes at a critical juncture in the nearly three-year conflict, with both sides seeking to strengthen their negotiating hand ahead of US President-elect Donald Trump’s return to the White House on 20 January.

“At about 9 a.m. Moscow time (0600 GMT), in order to halt the advance of Russian troops in the Kursk direction, the enemy launched a counterattack,” the Russian defense ministry said.

The Ukrainian army did not comment on the operation, simply saying in its daily report that fighting was under way in the Kursk region without elaborating.

Ukraine used two tanks, a dozen armored vehicles and a demolition unit in the assault, which was directed towards the village of Berdin — about 15 kilometers northeast of Sudzha, Moscow said.

“The operation to destroy the Ukrainian army formations continues,” it added.

Pro-Kremlin military bloggers acknowledged the Russian army had come under pressure but said Moscow was fighting back.

“The main events of the next attempted offensive by the Ukrainian army are clearly still ahead of us,” influential pro-Russian Telegram channel Rybar said.

Images purportedly showing a column of Ukrainian armored vehicles driving through the snow were shared by pro-Russia military blogger Dva Mayora on Telegram.