President Volodymyr Zelensky said on Saturday he was visiting "advanced positions" of Ukraine's special forces near the hotspot of Bakhmut as Kyiv ramps up its counter-offensive.
"The Bakhmut direction, advanced positions of the Special Operations Forces," Zelensky said on messaging app Telegram.
"I am here to congratulate our warriors on their professional day, to honour their strength."
Zelensky said he was not at liberty to disclose details of the special forces' current operations.
He said he heard a commander's report and spoke with the troops, praising their "truly heroic" performance.
Ukraine last month began its highly anticipated fightback after stockpiling Western weapons and building up its offensive forces.
Kyiv has however admitted difficult battles and called on the United States and other allies to provide long-range weapons and artillery.
Ukrainian authorities have said Kyiv's troops are gradually moving forward near the eastern city of Bakhmut, which Russian forces seized in May.