The Ukrainian armed forces made the biggest breakthrough on the southern front since the beginning of the war.

Troops advanced on the front line in the Dnipro River area of ​​the Kherson region on Monday.

Thousands of Russian soldiers were at risk of being cut off from the supply lines.

The government in Kyiv initially only commented cautiously on what was going on in the war.

But Russian sources reported Ukrainian armored forces advancing south along the course of the river.

An adviser to the Kyiv Interior Ministry, Anton Gerashchenko, released a video showing Ukrainian soldiers raising their national flag in the village of Solota Balka.

The area lies between the cities of Cherson and Zaporizhia, whose regions Russian President Vladimir Putin declared on Friday as annexed.

"The information situation is tense, let's put it that way, because there have indeed been breakthroughs," said Vladimir Saldo, Russia's installed governor in the occupied parts of Kherson, on Russian state television.

Saldo specifically named the area around the village of Duchany on the banks of the Dnipro.

"There are settlements that are occupied by Ukrainian troops." Duchany is about 30 kilometers south of the previous line of the front before the Ukrainian breakthrough.

This was the strongest advance of Ukrainian troops in the south.

After the start of the Russian war of aggression, the area around Cherson was marked by a rigid front line for a long time.

Rob Lee of the American think tank Foreign Policy Research Institute quoted Russian bloggers as reporting that their troops had withdrawn to Duchany, about 40 kilometers further south on the banks of the Dnipro.

"When so many Russian channels sound the alarm, it usually means they're in trouble," Lee wrote on Twitter.

Should Ukrainian forces make further advances on the banks of the river, thousands of Russian soldiers could be trapped.

The Dnieper is very wide in places, and Ukraine destroyed most of the bridges.

By Monday afternoon, the Ukrainian Ministry of Defense had only confirmed the capture of a town about 20 kilometers from the previous front line.

Serhiy Chlan from the Kherson Regional Council listed other towns that had been taken by Ukrainian troops, including Soloto Balka.

"It means that our forces are advancing with strength on the banks of the Dnipro, closer and closer to Beryslav," Gerashchenko of the Interior Ministry in Kyiv said.

"Officially, there is no such information yet, but the panicking (Russian) pages on social media (...) absolutely confirm these photos."