Russia has, since its 2022 invasion, been seeking to take the whole of the Donbas area in eastern Ukraine, where Kyiv's forces have been pushed back towards a line of cities in grinding fighting.
Kyiv has also reported some gains in the deadliest war in Europe since World War II.
Top Ukrainian commander Oleksandr Syrskyi said in mid-April Kyiv's forces had regained control of nearly 50 sq km of its territory in March.
"Since the beginning of this year, a total of 80 settlements and more than 1700 square kilometres of territory have come under our control," Valery Gerasimov, Chief of the General Staff of the Russian Armed Forces, said in footage released by the defence ministry on Tuesday.
Reuters was unable to verify the battlefield accounts, and a spokesperson for Ukraine's General Staff said he would not comment on the claim.
Pro-Ukrainian maps indicate Russia has taken about 600 sq km in 2026.
Gerasimov said Russia's southern grouping of forces was attacking the Donetsk fortress belt comprising the cities of Sloviansk, Kramatorsk and Kostiantynivka, and Russian forces were about seven to 12km from Sloviansk and Kramatorsk.
Russian units were already fighting in parts of Kostiantynivka, he said. In addition, Gerasimov said, Russian forces were advancing in Sumy in the north and Kharkiv in the northeast to create what he called "a security zone".
Kyiv's military said on Tuesday its forces had stopped two Russian attempts to advance around villages near Sloviansk over the past 24 hours, and Moscow had carried out 19 attacks near Kostiantynivka and eight nearby villages.
It also said Russian forces had made five attempts to break Ukrainian defences around several settlements near the Russian border in the Kharkiv region.
According to Russian estimates, Russia controls about 90 per cent of Donbas, about 75 per cent of the Zaporizhzhia and Kherson regions, and slivers of the Kharkiv, Sumy, Mykolaiv and Dnipropetrovsk regions in Ukraine.
Russia also controls Crimea, which it annexed in 2014 after earlier fighting. The Black Sea peninsula is internationally recognised as part of Ukraine by most countries.
Pro-Ukrainian maps show Russia controls 116,793 sq km, or 19.35 per cent, of Ukraine, but that Russia's advance has slowed in 2026.
