KYIV, Oct 3 (Reuters) – Ukrainian forces achieved their biggest breakthrough in the south of the country since the war began, bursting through the front and advancing rapidly along the Dnipro River on Monday, threatening to encircle thousands of Russian troops.

Kyiv gave no official confirmation of the gains, but Russian sources acknowledged that a Ukrainian tank offensive had advanced dozens of kilometers (miles) along the river’s west bank, recapturing a number of villages along the way.

The breakthrough mirrors recent Ukrainian successes in the east that have turned the tide in the war against Russia, even as Moscow has tried to raise the stakes by annexing territory, ordering mobilisation and threatening nuclear retaliation.

“The information is tense, let’s put it that way, because, yes there were indeed breakthroughs,” Vladimir Saldo, the Russian-installed leader in occupied parts of Ukraine’s Kherson province told Russian state television.