"Infuriate Moscow, impress Europe, save her country once again - that’s who Maia Sandu is," Tusk said in an X post on Monday.
"A great leader and a brave nation," he added.
Sandu said on Monday that Moldovans had won a crucial first battle shaping their future, as a referendum on the country's aspirations to join the EU was on course to yield a narrow majority "yes" vote of just over 50 percent, the Reuters news agency reported.
Speaking at a news briefing, the Moldovan leader condemned an outside attempt to buy votes to influence the referendum, calling it an attack on the country's sovereignty, according to Reuters.
She added that Moldova needed to do more to combat corruption, it reported.
Tusk last month visited the Moldovan capital Chișinău for talks with Sandu, Prime Minister Dorin Recean and parliamentary Speaker Igor Grosu. He also addressed a special session of the Moldovan parliament.
Polish Prime Minister Donald Tusk and Moldovan President Maia Sandu meet in Chișinău on September 4, 2024. Photo: PAP/Rafał Guz
The Polish leader at the time underscored Moldova's significance to regional security, public broadcaster Polish Radio’s IAR news agency reported.
He told reporters that his visit ahead of Moldova’s October 20 presidential election and EU membership referendum aimed to bolster the country’s pro-European ambitions.
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Source: IAR, PAP
Click on the audio player above for a report by Radio Poland's Marcin Matuszewski.