President Volodymyr Zelensky said Ukraine's military had won back dozens of towns in the past week as he ruled out holding peace talks with Vladimir Putin.
In his nightly address, the Ukrainian leader said that the army had made major and rapid advances against Russian forces in the south and east which Putin had declared annexed.
"This week alone, since the Russian pseudo-referendum, dozens of population centres have been liberated. These are in Kherson, Kharkiv, Luhansk and Donetsk regions all together," he said.
"Our soldiers do not stop. And it's only a matter of time before we expel the occupier from all of our land."
In a decree on Tuesday, Zelensky also said that any talks with Putin were "impossible" but left the door open to discussions with a new Russian leader.
At the same time the Kremlin has said that it "takes two sides to negotiate" over the possibility of talks taking place.
Russia held a lavish ceremony to say it had annexed the four regions of Kherson, Kharkiv, Luhansk and Donetsk after referendums which were widely derided as being shams with people coerced into voting.
Putin has indicated that he would use nuclear weapons to defend Russian territory and the fear has been that having claimed these regions to now be under the Russian flag, whether he would use this as an excuse to use the weapons.
But it has not stopped Ukrainian forces fighting to win back ground and Zelensky named eight small towns in Kherson in the south as recently having been recaptured.
A video released by the Ukraine defence ministry appeared to show the Ukrainian flag being raised over one of those communities, Davydiv Brid, in Kherson.
Ukrainian forces retook several villages in an advance along the strategic Dnipro River on Monday, Ukrainian officials and a Russian-backed leader in the area said.
In the east, Ukrainian forces have been expanding an offensive after capturing the main Russian bastion in the north of Donetsk, the town of Lyman.
Russian forces in the Donetsk and Kherson regions have been forced to retreat in recent days and appear to be struggling to halt an increasingly Western-equipped Ukrainian army.
"In some areas of the front line it was possible to extend the area we hold from between 10 to 20 km," the southern Operational Command of the Ukrainian Armed Forces (UAF) said.
Russian forces were destroying their reserves of ammunition and trying to destroy bridges and crossings in order to slow the Ukrainian advance, the UAF said in its daily report.
In the past 24 hours, Russia had lost 31 servicemen, more than 40 pieces of equipment, including eight tanks, 26 armoured vehicles, and a large calibre howitzer, it said.
Moscow hopes a "partial mobilisation" it announced weeks ago can help reverse a series of battlefield setbacks.
Defence Minister Sergei Shoigu was cited by the RIA news agency on Tuesday as saying that Russia had so far called up more than 200,000 reservists out of a planned 300,000 men.
Many Russian men have fled the country rather than fight in Ukraine, however, and Russian lawyers say they are working to advise men who want to avoid being drafted. Some Russians are making journeys of thousands of miles by car, train and plane to escape.
