Ukraine said Tuesday it was fighting off dozens of attacks, after President Volodymyr Zelensky said Russian forces were exploiting delays in Western military aid and called the situation "extremely difficult".
A heightened Russian offensive in eastern and southern Ukraine saw them capture the key town of Avdiivka last week in a boost ahead of the second anniversary of the February 2022 invasion.
The surge comes as Ukraine marks the 10th anniversary of the shooting of dozens of protesters in Kyiv during a revolution that toppled the country's Moscow-backed leadership.
The uprising also signalled the start of Russia's annexation of Crimea in the south of Ukraine and a pro-Russian separatist movement in the east.
"It has been 10 years since the attempts to destroy us and our independence," Zelensky said on Facebook on Tuesday.
"But we stood firm 10 years ago and continue to do so today," he said.
Presidency chief Andriy Yermak said Russia "sought to turn us into its colony, but did not achieve its goal. We will win."
The Ukrainian army general staff said there had been "81 combat clashes" over the past 24 hours, adding that Russian forces had carried out 87 air strikes.
Five civilians died in a strike on a village near the Russian border in Ukraine's Sumy region, the army said.
The Ukrainian military has said it is critically short of ammunition and shells, worsened by the holdup of a $60 billion US aid package.
"The situation is extremely difficult in several parts of the front line, where Russian troops have concentrated maximum reserves," Zelensky said Monday after visiting frontline troops in the Kharkiv region.
Russian troops "are taking advantage of the delays in helping Ukraine," Zelensky added, highlighting shortages of artillery, frontline air defence and longer-range weapons.
US President Joe Biden told Zelensky on Sunday that he was "confident" the Republican-dominated US Congress would approve the critically needed aid.
Ukrainian Prime Minister Denys Shmygal said Tuesday he also believed Congress would come through after it returned from recess and that his country would "continue our fight" with international support.
"I believe the United States will support Ukraine also, like the European Union, like Japan, like all the G7 countries and the IMF and all international financial organisations," Shmygal told a press conference in Tokyo when asked about "Ukraine fatigue" in the international community.
"So we can't speak about fatigue, because it's an existential war -- you can't be fatigued when you're fighting for your future, for your life... for global security order," he said.
Biden has said another Ukrainian town could fall to Russia without the aid and Ukrainian commanders have predicted that Russia will move troops from Avdiivka to other parts of the front line.
