"In fact, our forces are depriving the occupier (Russia) of the opportunity to carry out a full-fledged offensive operation, which they had been planning for a long time and counting on," he said in a video address.
Ukrainian forces have taken back 160 square km since the start of the operation, he said, adding that more than 170 square km and another nine settlements had been "cleared of the occupiers".
He did not specify when the operation began.
He described fighting as heavy in the area of Dobropillia, an area where there were rapid Russian advances in mid-August, and around the hub of Pokrovsk.
Reuters could not verify the battlefield situation in the war raging since Russia's full-scale invasion in February 2022.
The Donetsk region, which is only partially occupied by Russia but which the Kremlin wants Ukraine to abandon before any peace settlement, remains the site of the most intense fighting.
On Thursday, a Russian guided bomb strike killed five civilians in Kostiantynivka, 40km from Dobropillia, local officials said.
Russian forces have come within 8km of the city, which has long served as a crucial logistics hub for Ukrainian troops defending a swath of the front line.
Russia handed over more soldiers' remains to Ukraine, officials said on Thursday.
Ukraine received 1000 fallen soldiers, according to the staff responsible for prisoner of war affairs.
The handover was mediated by the International Red Cross.
Russian military bloggers wrote that Russia received the remains of 24 soldiers in return, although this figure has not been officially confirmed.
Ukraine has been defending itself against the Russian invasion for more than three and a half years.
Since the beginning of the year, Ukraine has received more than 13,000 soldiers' remains from the Russian side.
On the other side, the number is significantly lower.
Due to the slow but steady advance of Kremlin troops, only a few Russian casualties remain on the Ukrainian side of the front line.
US President Donald Trump on Thursday said that resolving the war in Ukraine has been more complex than he had expected and that Russian President Vladimir Putin had let him down.
"He's let me down. He has really let me down," Trump said in a news conference alongside UK Prime Minister Keir Starmer.
In their meeting, the two discussed ways to increase military support for Ukraine, Starmer said.
Putin said on Thursday that more than 700,000 Russian soldiers are deployed on the Ukrainian front line.
Putin made the comment during a televised meeting with top Russian MPs.
with DPA
