Ukrainian troops continue to put pressure on the retreating Russian forces, trying to hold on to their sudden momentum that has resulted in large territorial gains.

Fresh yellow-and-blue flags fluttered from the tallest buildings left in partially destroyed towns around Ukraine’s second-largest city, Kharkiv, while Ukrainian soldiers inspected charred Russian tanks abandoned along the way.

“From the beginning of September to today, our soldiers have already liberated more than 6,000 square kilometers of Ukraine’s territory – in the east and south. The movement of our troops continues,” said Ukrainian President Volodymyr Zelenskyy in his late night address late Monday.

Many of the claims of military success could not be independently verified.

British intelligence rubbed salt in Russia’s wounds, saying that one of Moscow’s leading forces, the 1st Guards Tank Army, was “severely degraded” during the invasion and that “Russia’s conventional fighting force designed to counter NATO is severely weakened”. .

They added: “It will probably take years for Russia to rebuild this capability.”

However, the retreat did not prevent Russia from attacking Ukrainian positions. Early Tuesday it shelled the town of Lozova in the Kharkiv region, killing three people and wounding nine, regional governor Oleh Syniehubov said.

The Nikopol area, which is across the Dnieper from the Zaporizhzhia nuclear power plant, was shelled six times during the night, but no casualties were immediately reported, regional governor Valentyn Reznichenko said.

The continued shelling has left Europe’s largest nuclear facility in a precarious position.

Mr Zelensky specifically criticized Russia for targeting energy infrastructure in its attacks in recent days.

“Hundreds and thousands of Ukrainians found themselves in the dark – without electricity. Homes, hospitals, schools, community infrastructure… places that have absolutely nothing to do with the infrastructure of our country’s armed forces.”

He said it could only indicate one thing. “This is a sign of the desperation of those who invented this war. This is how they react to the defeat of Russian forces in the Kharkiv region. They cannot harm our heroes on the battlefield,” he said.

Ukrainian military intelligence said Russian troops surrendered en masse. An aide to Ukraine’s president said there were so many prisoners of war that the country had no space to hold them.

The counteroffensive left the Kremlin for an answer to its biggest military defeat in Ukraine since Russian forces withdrew from areas near Kyiv after a botched attempt to capture the capital earlier in the invasion.

Russia’s Defense Ministry acknowledged the backlash in a map showing its troops being pushed back along a narrow stretch of land bordering Russia – a tacit admission of large Ukrainian gains.

It was not yet clear whether the Ukrainian blitz could signal a turning point in the war. Momentum has swung back and forth before, but rarely with such a large and sudden swing.

Some in Russia blamed Western weapons and fighters for the casualties.

“It was not Ukraine that attacked Isium, but NATO,” was the headline in the state-supported newspaper Komsomolskaya Pravda about one of the areas from which Russia claims it has withdrawn troops.

Elsewhere, residents of a Russian village just across the Ukrainian border were evacuated after one person was killed by shelling from Ukrainian troops, according to Russian news agency Tass.

The report quoted the head of the local administration in Logachevka as saying Ukrainian troops opened fire at a border checkpoint.