Hundreds of thousands have been killed and millions forced from their homes since Russia invaded in February 2022.
The Ukraine war front line remained largely frozen in June, extending a longer-term trend of stalled Russian momentum, an analysis of data from the Institute for the Study of War (ISW) carried out by the AFP news agency showed on Friday.
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The June data showed a Russian net gain of 30 square kilometres, focused in the northeastern Kharkiv region.
But those gains were largely down to previous Russian incursions being upgraded to advances, as more evidence came to light, said the ISW.
Ukrainian forces gained 11 square kilometres in the southern Zaporizhzhia region and 18 square kilometres in the central Dnipropetrovsk region.
"The extent and scope of the ongoing Ukrainian counterattacks in these oblasts are unclear," said the ISW's Geospatial Intelligence Team.
"The outcomes from these continuing combat operations remain unclear and will likely be reflected in the data in the coming weeks," it added.
Moscow lost around 403 square kilometres in April and May. Russia's advance has slowed since late 2025, hobbled by the increasing effectiveness of Ukraine's frontline and mid-range drone strikes.
April was the first month in which its forces gave up more ground than they captured for two and a half years and Ukraine built on those gains in May.
Russian forces have advanced an average of 15 square kilometres per month so far in 2026, compared with 405 square kilometres per month in 2025.
The estimates exclude advances claimed by Russia but that the ISW has neither confirmed nor denied.
The ISW works with the Critical Threats Project, part of the American Enterprise Institute, another US think tank specialising in conflict analysis.
Moscow occupies just over 19% of Ukraine.
That includes around 7%, Crimea and parts of the industrial Donbas region, that was already under Russian or pro-Russian separatist control before the February 2022 full-scale invasion.
Most of Russia's advances were made during the first weeks of the conflict.
Hundreds of thousands have been killed and millions forced from their homes since Russia invaded in February 2022.
The war, Europe's deadliest since World War II, has caused more than 2 million military casualties, with Moscow's forces bearing the brunt of the losses, according to a study published by a US think tank on Wednesday.