Ukraine, with momentum, determined to liberate more territory from Russian forces

Ukrainian troops continued to pile unrelenting pressure on retreating Russian forces on Tuesday, seeking to hold on to their sudden momentum that has produced major territorial gains.

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

"From the beginning of September until today, our soldiers have already liberated more than 6,000 square kilometres of the territory of Ukraine — in the east and south. The movement of our troops continues," said Ukrainian President Volodymyr Zelenskyy in his nightly address late Monday.

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

British intelligence said that one of Moscow's premier forces, the 1st Guards Tank Army, had been "severely degraded" during the invasion and that "Russia's conventional force designed to counter NATO is severely weakened. It will likely take years for Russia to rebuild this capability."

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Fighting was still raging in the northeastern Kharkiv region, Deputy Defence Minister Hanna Malyar told Reuters on Tuesday, saying Ukraine's forces were making good progress because they are highly motivated and their operation is well-planned.

"The aim is to liberate the Kharkiv region and beyond — all the territories occupied by the Russian Federation," she said on the road to Balakliia, a crucial military supply hub recaptured by Ukrainian forces late last week that lies 75 kilometres southeast of Kharkiv, Ukraine's second-largest city.

The retreat didn't stop Russia from pounding Ukrainian positions, however. Early Tuesday, it shelled the city of Lozova in the Kharkiv region, killing three people and injuring nine, said regional Gov. Oleh Syniehubov.

The Nikopol area, which is across the Dnieper River from the Zaporizhzhia nuclear power plant, was shelled six times during the night but no injuries were immediately reported, said regional Gov. Valentyn Reznichenko. Continued shelling has left Europe's largest nuclear facility in a precarious position.

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Zelenskyy specifically criticized Russia for targeting energy infrastructure in its attacks over the past days.

"Hundreds and thousands of Ukrainians found themselves in the dark — without electricity. Houses, hospitals, schools, communal infrastructure sites that have absolutely nothing to do with the infrastructure of the armed forces of our country," he said.

"This is a sign of the desperation of those who contrived this war."