CNN  — 

Ukrainian officials say the military has made sweeping gains in a counteroffensive in the northeastern Kharkiv region, with President Volodymyr Zelensky asserting that a key city in the region has been reclaimed by Ukrainian forces and that Russian offensives across the country are being repelled.

Zelensky posted a video on his social media accounts with Ukrainian soldiers standing above a building in the key Kharkiv city of Balakliia, which was under Russian occupation for six months, alongside the Ukrainian flag.

“The order is fulfilled. Russian occupational troops have withdrawn,” one of the soldiers says in the video.

A video posted on Ukrainian President Volodymyr Zelensky Facebook page on Thursday September 8, claims his soldiers have retaken the key Kharkiv city of Balakliia.

Ukrainian troops have also reached the city of Kupyansk in the Kharkiv region – a key logistics and supply hub for Russian forces – according to a photo showing Ukrainian soldiers holding a flag in front of a signpost at the southern entrance of the city, geolocated by CNN. Ukrainian forces have not yet retaken the city, which is roughly 70 miles (112 kilometers) east of Kharkiv.

Russian military bloggers and analysts have said that Ukrainian forces’ push towards Kupyansk aims to cut off supply lines to the strategic city of Izium to the south. Usually supportive of the Russian campaign in Ukraine, many have criticized Moscow’s failure to predict a Ukrainian counteroffensive in Kharkiv, and the lack of troops and equipment in numbers capable of stopping a Ukrainian push.

In a nightly address Thursday, Zelensky claimed the country’s military had retaken more than 1,000 square kilometers of territory since the beginning of the month. Oleksii Hromov, the deputy head of the main operations directorate of the General Staff of the Armed Forces of Ukraine, said Ukrainian forces were able to advance 50 kilometers (about 31 miles) in the Kharkiv region and liberate “more than 20 settlements.”

Through geolocation and the statements of the Ukrainian military, independent analysts and Russian military bloggers, it’s estimated that Ukrainian forces have taken well over 400 square kilometers of territory this week in the Kharkiv region.

Meanwhile, some Russian troops in the Kharkiv region have deserted and abandoned their uniforms due to Russia’s “significant losses,” the General Staff of the Ukrainian Armed Forces said, adding that the soldiers are hoping to blend in while wearing civilian clothing.

“Personnel of the occupying forces in civilian clothes resort to desertion and try to return to the territory of the Russian Federation,” the General Staff said in a situational update Friday, claiming that 15 such cases had been observed.

The Intelligence Directorate of the Ukrainian Defense Ministry said that the Russian 202nd Motorized Rifle Regiment, “located in the Kharkiv region, withdrew from their positions and moved to the nearest forest. The unit was left without commanders and communications.”

The Directorate claimed that Russian soldiers were “calling to relatives with requests to contact the command and find out where they should go next. Some of them ask their wives to contact the hotlines of the Ministry of Defense of Russia and the Red Cross with the demand to remove them from the territory of Ukraine.”

It provided no evidence for the assertion.

Counteroffensives on two fronts

While the southern front, in Kherson region, looks set to be one of the main theaters of conflict as the war heads towards winter, a new Ukrainian push in Kharkiv could stretch Russian forces across two disparate locations.

In recent weeks, Russia redeployed some forces to the south to bolster its ranks ahead of the Ukrainian counteroffensive in Kherson region, according to Ukrainian officials and footage of equipment moving through Crimea geolocated by CNN.

On Wednesday, Zelensky thanked units stationed in southern Ukraine what he called “extremely successful hits” on occupying Russian forces, while the simultaneous counterattack was launched in the north.

“The more difficult it is for the occupiers, the more losses they have, the better the positions for our defenders in Donbas will be, the more reliable the defense of Zaporizhzhia, Mykolaiv, and the cities of Dnipropetrovsk region will be, the faster we will be able to liberate the Azov region and the entire south,” he said.

Ukraine continues to press on with its southern counteroffensive; Ukrainian forces are making gains in the south, with the ambitious goal of taking back most of the Russian-occupied region of Kherson by the end of the year, senior US officials and Ukrainian officials told CNN on Wednesday.

The last week has seen the most ambitious ground assaults by the Ukrainians since the beginning of the invasion, following sustained attacks on command posts, ammunition stores, and fuel reserves far behind the front lines, according to geolocation of video and satellite imagery.

The US has observed Ukrainian forces achieve some success in attacking Russian supply lines, with the intention of cutting off and isolating Russian troops currently deployed west of the Dnipro River, according to a senior US official.

Teele Rebane, Oleksandra Ochman, Gianluca Mezzofiore and Rob Picheta contributed reporting.