The US think tank made the assessment in its latest report on the war in Ukraine, published on Sunday night.
Ukrainian forces on Sunday continued positional engagements with Russian troops along the Kupaynsk-Svatove-Kreminna line, in the eastern Luhansk region, but there were "no confirmed changes to the frontline in this area," the ISW reported.
Ukrainian and Russian units also clashed near Bakhmut and near Avdiivka, in the next-door Donetsk province, also without "confirmed changes to the frontline," according to US analysts.
Russia was attacking towards Avdiivka "from all directions," including "several dozen" air strikes per day, according to city officials.
In addition, Ukrainian troops on Sunday fought with Russian forces in the Donetsk-Zaporizhzhia region border area, and there were also positional battles near Robotyne in Zaporizhzhia, without "confirmed changes to the frontline" in either area, the ISW said.
Ukraine on Sunday continued to hold positions on the eastern (left) bank of the Kherson province, amid battles with Russian forces near Krynky, and "the frontline has not changed" in the area, according to the US think tank.
In all, Ukrainian and Russian troops clashed 29 times on Sunday, the General Staff in Kyiv said.
Monday is day 684 of Russia’s war on Ukraine.
Russia invaded Ukraine on February 24, 2022, launching the largest military campaign in Europe since World War II.
Source: ISW, The General Staff of the Armed Forces of Ukraine