A Man uses his mobile phone as he stands on a bridge destroyed by a Russian Missile strike in Svyatohirsk
A Man uses his mobile phone as he stands on a bridge destroyed by a Russian Missile strike, amid Russia's attack on Ukraine, in Svyatohirsk, in Donetsk region, Ukraine, October 3, 2022. Reuters

Ukrainian forces have broken through Russia's defences in the south of the country while expanding their rapid offensive in the east, seizing back more territory in areas annexed by Moscow and threatening supply lines for Russian troops.

Making their biggest breakthrough in the south since the war began, Ukrainian forces recaptured several villages in an advance along the strategic Dnipro River on Monday, Ukrainian officials and a Russian-installed leader in the area said.

The southern breakthrough mirrors recent Ukrainian advances in the east, even as Moscow has tried to raise the stakes by annexing land, ordering mobilisation, and threatening nuclear retaliation.

In a sign Ukraine is building momentum on the eastern front, Reuters saw columns of Ukrainian military vehicles heading on Monday to reinforce rail hub Lyman, retaken at the weekend and a staging post to press into the Donbas region.

President Volodymyr Zelenskiy said Ukraine's army had seized back towns in a number of areas, without providing details.

"New population centres have been liberated in several regions. Heavy fighting is going on on several sectors of the front," Zelenskiy said in a video address.

Ukrainian troops recaptured the town of Dudchany along the west bank of the Dnipro River, which bisects the country, Vladimir Saldi, the Russian-installed leader in occupied parts of Ukraine's Kherson province, told Russian state television.

"There are settlements that are occupied by Ukrainian forces," Saldi said.

Dudchany is around 30 km (20 miles) south of where the front stood before Monday's breakthrough, indicating the fastest advance of the war so far in the south. Russian forces there had been dug into heavily reinforced positions along a mainly static front line since the early weeks of the invasion.

While Kyiv has yet to give a full account of the developments, Ukrainian military and regional officials did release some details.

Soldiers from Ukraine's 128th Mountain Assault Brigade raised the country's blue and yellow flag in Myrolyubivka, a village between the former front and the Dnipro, according to a video released by the Defence Ministry.

Serhiy Khlan, a Kherson regional council member, also listed four other villages recaptured or where Ukrainian troops had been photographed.

"It means that our armed forces are moving powerfully along the banks of the Dnipro nearer to Beryslav," he said.

Reuters was unable to independently verify the developments.

'ABILITY TO ATTACK'

The southern advance is targeting supply lines for as many as 25,000 Russian troops on the Dnipro's west bank. Ukraine has already destroyed the river's main bridges, forcing Russian forces to use makeshift crossings.

A substantial advance down river could cut them off entirely.

"The fact we have broken through the front means that... the Russian army has already lost the ability to attack, and today or tomorrow it could lose the ability to defend," said Oleh Zhdanov, a military analyst based in Kyiv.

Ukraine appears to be on course to achieve several of its battlefield objectives, giving Kyiv "a much better defensive position to ride out what probably will be a tamping down of the hot fighting over the winter," Celeste Wallander, a senior Pentagon official, said on Monday.

Since the start of September, Ukrainian forces have swiftly seized territory in the east to gain control of Russian supply lines, cutting off larger Russian forces and forcing them to retreat.

Just hours after a concert on Moscow's Red Square on Friday where Russian President Vladimir Putin proclaimed the provinces of Donetsk, Luhansk, Kherson and Zaporizhzhia to be Russian territory forever, Ukraine recaptured Lyman, the main Russian bastion in the north of Donetsk province.

That has opened the way for it to advance deep into Luhansk province, threatening supply routes to territory Moscow captured in some of the war's bloodiest battles in June and July.

Russia's flagging fortunes have led to a shift in mood on once triumphal state media, where talkshow hosts have been acknowledging setbacks and searching for scapegoats.

"For a certain period of time, things won't be easy for us. We shouldn't be expecting good news right now," said Vladimir Solovyov, the most prominent presenter on state TV.

The commander of Russia's western military district, which borders Ukraine, has lost his job, Russian media reported on Monday, the latest in a series of top officials to be fired after the defeats.

(Writing by Rami Ayyub, Editing by Rosalba O'Brien)

A bridge destroyed by a Russian Missile strike is seen in Svyatohirsk
A bridge destroyed by a Russian Missile strike is seen amid Russia's attack on Ukraine, in Svyatohirsk, in Donetsk region, Ukraine, October 3, 2022. Reuters