The war between Russia and Ukraine appears to be entering a new phase after Kyiv dealt a big blow to Moscow's grip on parts of the east with a fast-moving offensive that saw Ukrainian troops enter the strategic city of Izium after six months of occupation.
When Ukrainian forces entered the city of Izium on Saturday, it was more than a significant military victory.
It was a sign that the Russian troops are scrambling to hold onto the territory they captured over the past six months, reported CNN.
Russian forces were forced to evacuate the strategic eastern city just five days after Ukrainian forces began a new offensive eastward through the Kharkiv region.
"Russians escaped and left weapons and ammo behind. The city centre is free," a spokesperson for the Bohun Brigade of the Land Forces of Ukraine said in a statement Saturday afternoon.
Ukrainian forces have liberated the settlement of Chkalovske in the Kharkiv region of Russian troops, President Volodymyr Zelenskyy said on Telegram on Sunday.
"Another freed settlement! Thanks to the 14th separate mechanized brigade named after Prince Roman the Great, the Ukrainian flag returned to Chkalovske, Kharkiv region," Zelenskyy said.
In his daily video message late on Friday, Zelenskyy said that the Armed Forces of Ukraine had liberated and taken control of more than 30 settlements in the Kharkiv region.
The last five days have seen the most ambitious ground assaults by the Ukrainians since Russia launched its full-scale invasion in late February.
'Weapons, weapons, weapons have been on our agenda since spring. I am grateful to partners who have answered our call: Ukraine's battlefield successes are our shared ones. Three agenda items now are schedule, schedule, and schedule. Prompt supplies bring victory and peace closer,' tweeted Dmytro Kuleba, Minister of Foreign Affairs of Ukraine.
Video and satellite images geolocated by CNN show the advances have involved sustained attacks on command posts, ammunition stores, and fuel reserves far behind the front lines.
A senior United States official said Ukrainian forces had achieved some success in attacking Russian supply lines, with the intention of cutting off and isolating Russian troops west of the Dnipro River.
Saturday's rapid advance did not end with Izium, as Ukraine appeared to have opened a new front against Russian defences on the border of the Donetsk and Luhansk regions, reported CNN.
Ukrainian forces continue to make 'significant gains' in the Kharkiv region, the United Kingdom's defence ministry tweeted Sunday.
It said that while Russia has 'likely withdrawn units from the area', fighting continues 'around the strategically important cities of Kupiansk and Izium'.
The head of the regional military administration for Luhansk, Serhiy Hayday, indicated the city of Lysychansk was the target of the new offensive.
Lysychansk was the last city in the Luhansk region in eastern Ukraine to fall under Russian control in July, after weeks of intense fighting.
Hayday told CNN on Saturday 'the occupiers, including both the collaborators and the military, are running away in a hurry'.
"Locals have videos and photos proving that," Hayday said.
He said the visual evidence could not be shared for security reasons.
Oleksiy Reznikov, the Ukrainian defence minister, said that Ukraine's allies are 'amazed' by the recent successes of the country's military.
Speaking at the end of a meeting of the Ukraine Defense Contact Group in Ramstein Air Base, Germany, Reznikov said Ukraine's 'partners were positively amazed by the dynamics of our troops' activities' in the south and east of the country.
Meanwhile, the Zaporizhzhia nuclear power plant has been shut down after it was reconnected to the power grid, Ukraine's nuclear energy agency said Sunday.