Russia controls an area of land the size of two football fields every minute in Ukraine.
Vladimir Putin's forces are advancing the fastest since the invasion began in 2022.
But it would take more than a year at the current rate to control the rest of Donetsk Oblast, which is Moscow's minimum goal.
The US-based Institute for the Study of War said Kremlin forces captured about 8.5 square miles a day this month, even though America gave Kiev permission to hit Russia with long-range missiles.
Russian forces advanced around Kubyansk, in the northeastern Kharkiv province, and Khorakov in the southern Donbass.
But attackers are turning away from “Ukrainian strong points” such as well-fortified cities, which they “cannot capture as quickly,” the Institute for the Study of War said.
Read more about the Ukraine war
British Defense Secretary John Healey warned that the 600-mile front line was the most unstable since February 2022.
But the rate of Russian advance is nowhere near its peak of 490 square miles per day—or 125 steps per minute—in the first weeks of the war.
The ruble fell to its lowest level since March 2022 despite recent gains on the battlefield.
Ukraine continued to bomb targets in Russia with US-made ATACMS missiles.
Russia claimed the missiles hit an air unit in Kursk and the nearby Kursk Vostochny Airport, which hosts Su-30 fighter jets.
Moscow vowed to respond.
Last week, it launched an experimental medium-range hypersonic ballistic missile, drawing condemnation from the West.