The Ukrainian military said on Monday that it had gained more ground against Russian forces over the past day, suggesting a lightning advance in the country’s northeast still had room to run.

After a dramatic weekend offensive that recaptured hundreds of square miles of territory, the army said that it had advanced into an additional 20 Ukrainian towns and villages over the past 24 hours that had been under Russian control.

The claim could not be independently verified. Retreating Russian forces have retaliated with longrange missile strikes and air raids, Ukrainian and American officials said.

Late on Sunday, Moscow attacked infrastructure facilities in Kharkiv, leaving many civilians without power and water.

The services were mostly restored by Monday morning, the Ukrinform news agency reported.

Russia’s pell-mell retreat has rattled Kremlin cheerleaders and amplified voices in the West demanding that more weapons be sent to help Ukraine win. Russia’s defence ministry on Sunday released a map that showed its forces had withdrawn to the eastern side of the Oskil River, about 10 miles east of the city of Izium, an important logistics hub for Moscow that its troops abandoned on Saturday.

The map indicated that Ukrainian forces had driven Russian troops from almost all of the Kharkiv region. For the US, the advance was a heartening development and suggested that Russian troops were in significant disarray.

But senior White House officials urged caution, voicing doubts about the capacity of Ukrainian forces to push Russia back to the lines that existed on February 23, the day before the invasion.

New York Times News Service