Ukrainian troops have piled pressure on retreating Russian forces, pressing deeper into occupied territory and sending more Kremlin troops fleeing ahead of a counteroffensive that has inflicted a stunning blow on Moscow’s military prestige.

As the advance continued, Ukraine’s border guard services said the army had taken control of Vovchansk — a town two miles from Russia that was seized on the first day of the war.

Moscow acknowledged that it had withdrawn troops from areas in the north-eastern region of Kharkiv in recent days.

Russian troops were also abandoning the southern city of Melitopol and heading towards Moscow-annexed Crimea, the city’s pre-occupation mayor said.

Columns of military equipment were reported at a checkpoint in Chonhar, a village marking the boundary between the Crimean peninsula and the Ukrainian mainland, mayor Ivan Fedorov said.

Melitopol, the second-largest city in Ukraine’s southern Zaporizhzhia region, has been under Russian occupation since early March. Capturing it would give Kyiv the opportunity to disrupt Russian supply lines between the south and the eastern Donbas region, the two major areas where Moscow-backed forces hold territory.

It is not clear if the Ukrainian blitz, after months of little discernible movement, could signal a turning point in the nearly seven-month war.

But the country’s officials were buoyant, releasing footage showing their forces burning Russian flags and inspecting abandoned, charred tanks. In one video, border guards tore down a poster that read “We are one people with Russia”.

Ukraine’s American allies were careful not to declare a premature victory since Russian President Vladimir Putin still has troops and resources to tap.

In the face of Russia’s largest defeat since its botched attempt to capture Kyiv early in the war, Defence Ministry spokesman Igor Konashenkov said troops were hitting back with “massive strikes” in all sectors, but there were no immediate reports of a sudden rise in Russian attacks.

Late on Monday, President Volodymyr Zelensky said his troops had retaken more than 2,300 square miles in a matter of weeks.

Reports of chaos abounded as Russian troops pulled out, as well as claims that they were surrendering en masse.

Mr Zelensky said Ukrainian forces were carrying out “stabilisation measures” across recaptured territory in the south and east, and rounding up Russian troops, “saboteurs” and alleged collaborators.

In his nightly televised address, Mr Zelensky also pledged to restore normality in liberated areas.

“It is very important that together with our troops, with our flag, ordinary, normal life enters the de-occupied territory,” he said.

Ukrainian deputy defence minister Hanna Maliar said Kyiv is trying to persuade more Russian soldiers to give up, launching shells filled with flyers ahead of their advance.

“Russians use you as cannon fodder. Your life doesn’t mean anything for them. You don’t need this war. Surrender to Armed Forces of Ukraine,” the flyers read.

While dozens of towns and villages were liberated, authorities moved into several areas to investigate alleged atrocities against civilians by Russian troops.

The Kharkiv regional prosecutor’s office said four bodies bearing signs of torture were found in the village of Zaliznychne. It is not clear how many other places investigators have entered.

Oleksandr Shtupun, a spokesman for the Ukrainian military’s general staff, accused Russian forces of committing hundreds of war crimes in territory they once held.

He said the danger of minefields in liberated towns and villages remained high, and ammunition and high explosives have been strewn across 27,000 square miles.

“The defence forces are taking measures to return peaceful life to the liberated communities as soon as possible,” he added.

British intelligence said one premier Russian force, the 1st Guards Tank Army, had been “severely degraded” during the invasion and that conventional forces designed to counter Nato have been badly weakened.

“It will likely take years for Russia to rebuild this capability,” the analysts said.

The setback might renew Russia’s interest in peace talks, said Abbas Gallyamov, an independent Russian political analyst and former speechwriter for Mr Putin.

But even if the president were to sit down at the negotiating table, Mr Zelensky has made it clear that Russia must return all Ukrainian territory, including Crimea, Mr Gallyamov said.

“This is unacceptable to Moscow, so talks are, strictly speaking, impossible,” he said.

For talks to be possible, Mr Putin “would need to leave and be replaced by someone who’s relatively untarnished by the current situation”, such as his deputy chief of staff, the Moscow mayor or the Russian prime minister, Mr Gallyamov added.