Russia abandoned military strongholds in northeastern Ukraine on Saturday in an apparent rout of its front line positions, after Ukrainian forces pushed forward in a lightning advance that has left Moscow’s forces in disarray.

Russia’s defence ministry said its forces had pulled back from the strategic city of Izyum, claiming it had decided to “regroup” and transfer them south-eastwards to the Donetsk region.

The Russian retreat is one of President Vladimir Putin’s biggest setbacks since he ordered a full invasion of Ukraine on February 24, and could prove a turning point, involving the capture of thousands of Russian soldiers and their equipment.

“Since the beginning of September, about 2,000km of our territory have been freed,” Volodymyr Zelenskyy, Ukraine’s president, said in his daily evening video address to the nation.

“The Russian army is showing its best — showing its back . . . it is a good choice for them to run away. There is no place for the occupiers in Ukraine and there will be no place,” Zelenskyy said.

In an apparent bid to encourage more Russian soldiers to surrender, Zelenskyy promised that Ukraine would “guarantee” Russian soldiers who surrender fair treatment “in accordance with the Geneva Conventions”.

Videos posted on social media show bedraggled Russian troops who had abandoned their vehicles and positions in a hurry, leaving equipment and food behind. Locals cheered Ukrainian forces as they advanced through liberated villages.

“The world earlier didn’t think that the Russians could be beaten . . . Today the world has seen that it’s proven that the Russians can and should be beaten. We are doing that and will do that,” Oleksii Reznikov, Ukraine’s defence minister, said on Saturday during the Yalta European Strategy conference in Kyiv.

In comments to the Financial Times, Reznikov described the rapid counteroffensive that had taken Russian soldiers by surprise and led many to flee as being like a “snowball rolling down the hill, getting bigger and bigger.”

He claimed that Ukraine’s counter-offensive was also making steady progress in southern regions near the city of Kherson. “We are moving but probably a bit slower” than in the east, he said.

The Russian defence ministry made a rare statement on Saturday portraying the pullback from Balakliia and Izyum as a move intended to focus attention on a different frontline, rather than a defeat following the Ukrainian attack, which began on September 6.

“In order to achieve objectives . . . it was decided to regroup the Russian troops . . . to increase efforts in the Donetsk direction,” defence ministry spokesman Igor Konashenkov said. He added that to this end: “an operation was conducted over three days to wind down and transfer out” Russian troops in that area.

The announcement came soon after Ukrainian troops captured Kupyansk, north of Izyum, a road and rail hub supplying Russia’s defences across northeastern Ukraine. This has left thousands of Russian troops cut off from supplies across a stretch of the battleground where some of the most intense battles of the war have been fought.

Ukrainian officials have not yet officially confirmed the capture of Izyum, but videos on social media show Ukrainian troops raising the national flag on the outskirts. Some officials confirmed it had been liberated.

Annalena Baerbock, Germany’s foreign minister, said the Ukrainian advance was a moment of hope. “This is what we need,” she said speaking on a visit to Kyiv. “We know that the time between UN General Assembly and Christmas is crucial and weapons support is crucial and we will be at their side.”

Analysts said Kyiv’s attack had taken advantage of Russian defences that had been depleted after troops were sent south to fend off a separate Ukrainian offensive. As many as 10,000 Russian troops may be caught in the new manoeuvre, Lawrence Freedman, emeritus professor of war studies at King’s College London, estimated.

Despite stiffer Russian resistance in the south, Nataliya Humenyuk, spokesperson for Ukraine’s armed forces near Kherson, said on Saturday that government troops were also making significant gains in the region.

“There is an advance of our troops along the southern front along various sections, from two to several dozen kilometres,” she said.

Military analysts said Ukraine had launched the two, nearly simultaneous, offensives to overwhelm the Russian military’s centralised system of command, which struggles with multidirectional deployments.

“Russian generals are afraid to make mistakes . . . which leads to the centralisation of decision-making, because everybody’s trying to push decisions as much upwards as possible to avoid responsibility. That kills their ability to deal with multidirectional approaches,” said Andriy Zagorodnyuk, a former Ukrainian defence minister.

“So that is exactly what our armed forces are doing . . . attacking where Russians don’t expect and in more than one direction,” he told participants at the Yalta conference.

Ukrainian officials said government troops were also advancing towards towns further east, including Lysychansk, Lyman and Kreminna.

One military commentator, embedded with Russian troops, described it as a “catastrophe” and the “biggest Russian military defeat since 1943”.

Below: Counter-offensive on Friday 9 September. Reports on Saturday suggest Ukrainian forces have reached both Kupyansk and Izyum.

But amid a growing sense of euphoria in Kyiv, analysts warned against reading too much into early Ukrainian successes, as supply lines could become overstretched while the Russian army retains fearsome capabilities.

“They [the Russians] have very good electronic warfare. They have very good artillery. They do have a few high-tech weapons . . . So, you have got to be careful. You always have to respect the adversary,” General Wesley Clarke, a former supreme Nato commander, said.

Russia is reportedly sending in more troops. Ukraine’s general staff said that 1,200 Chechen soldiers had been deployed to reinforce Russian positions around Kherson. Videos posted on social media on Saturday also allegedly showed the Russian army helicoptering in fresh troops to reinforce Izyum.