Zelenskiy Says Ukrainian Troops In Full Control Of Strategic City Of Lyman.

A Ukrainian soldier takes down a Russian flag hoisted on a monument in Lyman on October 1.

Ukraine's president has declared that Ukrainian troops are in full control of the eastern city of Lyman, a strategic city in the Donbas region that Russian forces withdrew from a day earlier.

Volodymyr Zelenskiy made the brief comment in a video clip posted to his Telegram channel on October 2.

"As of 12:30 p.m., Lyman is fully cleared," he said. "Thank you to our soldiers. Glory to Ukraine."

The recapture of Lyman is the Ukrainian forces' most significant battlefield gain in weeks, and followed a counteroffensive in the Kharkiv region to the north that swept Russian forces and stunned many observers.

Lyman sits at a crossroads and a rail hub and analysts say Ukrainian troops will likely use the city as a staging post for further advances east.

The city had been the scene of intense fighting for days, with Ukrainian troops gradually encircling it and the estimated 5,000 Russian troops that were defending it.

Russia's Defense Ministry on October 1 said it was pulling troops out of the area "in connection with the creation of a threat of encirclement."

Unconfirmed reports said Russian forces there had suffered heavy casualties, and an unknown number of soldiers taken prisoner.

It was the latest setback for Russian President Vladimir Putin, coming the day after he proclaimed the annexation of four Ukrainian regions that have been partly occupied by Russian forces for months now.

The Donetsk region, where Lyman is located, is one of those four regions Putin claimed.

Kyiv and the West have condemned the annexation declaration as illegal and a farce.

"The liberation of this city in the Donetsk region is one of the key factors for the further de-occupation of the Luhansk region," Serhiy Hayday, the head of the Luhansk military administration, wrote on Telegram.

Putin’s declaration that Russia was annexing Donetsk, along with Luhansk, Kherson, and Zaporizhzhya, was a major escalation by the Kremlin. Observers said it signaled a further digging-in by the Russian leadership, dampening prospects for a peace deal.

Together with Crimea, which Moscow seized in 2014, the four regions make up around 20 percent of Ukraine, including some of its most industrialized territory.

Kyiv has said it will not negotiate with Moscow as long as Putin remains in power.

In the southern Ukrainian region of Kherson, Ukrainian forces have been waging a parallel counteroffensive that has so far yielded few of the dramatic gains seen in Kharkiv.

Experts say Russian commanders shifted some of their most experienced and capable units away from the Donbas to Kherson in August, in anticipation of a Ukrainian counteroffensive.

With reporting by Reuters