KYIV: Swiftly advancing Ukrainian troops were bearing down on the main railway supplying Russian forces in the east on Friday (Sep 9), after the collapse of a section of Russia's front line caused the most dramatic shift in the war's momentum since its early weeks.
In a video address, President Volodymyr Zelenskyy said that Ukrainian troops had "liberated dozens of settlements" and reclaimed more than 1,000 sq km of territory in the east and south in the past week.
Zelenskyy posted a video in which Ukrainian soldiers said they had captured the eastern town of Balakliia, which lies along a stretch of front stretching south of Kharkiv, Ukraine's second largest city.
The Ukrainian military said it had advanced nearly 50km through that front after an assault that appeared to take the Russians by surprise.
That would make it by far the fastest advance by either side in the war since Russia was forced to abandon its disastrous assault on the capital Kyiv in March.
Moscow has so far offered no official response to the reports of the breakthrough on the Kharkiv front.
Ukraine has yet to allow independent journalists into the area to confirm the extent its advances. But Ukrainian news websites have shown pictures of troops cheering from the top of armoured vehicles as they roar past street signs bearing the names of previously Russian-held towns, and Russian forces surrendering on the side of the road.
The Institute for the Study of War think-tank said that the Ukrainians were now within just 15km of Kupiansk, an essential junction for the main railway lines that Moscow has been using for months to supply its forces on the battlefields in the east.
Since Russia's forces were defeated near Kyiv in March, Moscow has waged a relentless war of attrition, using its firepower advantage to press slow advances by bombarding towns and villages. But that tactic depends on tonnes of ammunition a day reaching the front line by train from western Russia. Until now, Russia had successfully fended off all attempts by Ukraine to cut off the train line.
The Ukrainian general staff said early on Friday that retreating Russian forces were trying to evacuate wounded personnel and damaged military equipment.
"Thanks to skilful and coordinated actions, the Armed Forces of Ukraine, with the support of the local population, advanced almost 50km in three days," it said.
The surprise Ukrainian breakthrough in the east came a week after Kyiv announced the start of a long-awaited counteroffensive hundreds of kilometres away at the opposite end of the front in Kherson province in the south.
Ukrainian officials say that Russia moved thousands of troops south to respond to the Kherson advance, leaving other parts of the front line exposed and weakly defended.
"We found a weak spot where the enemy wasn't ready," presidential adviser Oleksiy Arestovych said in a video posted on YouTube.
Less information so far has emerged about the campaign in the south, with Ukraine keeping journalists away and releasing few details to keep its full plans secret.
Ukraine has been using new Western-supplied artillery and rockets there to hit Russian rear positions, with the aim of trapping thousands of Russian troops on the west bank of the wide Dnipro River and cutting them off from supplies.
Arestovych acknowledged that progress in the south had not yet been as swift as the sudden breakthrough in the east.
Russia's state news agency RIA quoted Russian-appointed Kherson authorities as saying that some Ukrainian troops were captured during the counterattack and an undisclosed number of Polish tanks they were using had been destroyed. Reuters could not verify those reports.
United States Secretary of State Antony Blinken visited Kyiv on Thursday and announced a package of US$2.2 billion in military financing for countries at risk of Russian aggression, nearly half of it for Ukraine. Washington also announced a separate US$675 million of new weapons for Ukraine.
North of the battlefield, Russia has continued firing at Kharkiv. Missiles struck multiple areas there on Thursday, causing widespread damage and casualties, according to the regional prosecutor's office.
"We are scared ... You can't get used to it, never," resident Olena Rudenko told Reuters.
Russia denied targeting civilians. Tens of thousands of people have been killed, millions have been driven from their homes and cities have been flattened since Moscow launched what it calls a "special military operation" in February to "disarm" Ukraine.