Tusk made his remarks on his Facebook profile after Syrian rebels declared Syrian President Bashar al-Assad's ouster after seizing control of Damascus on Sunday, forcing him and his family to flee after more than 13 years of civil war in a seismic moment for the Middle East.
The Islamist rebels also dealt a major blow to the influence of Russia and Iran in Syria in the heart of the region - allies who had propped up Assad during critical periods in the conflict.
World reacts to the toppling of Al-Assad's regime
Ukrainian foreign minister Andriy Sibiha has warned states allied with Russia that “[Putin] always betrays those who rely on him.”
Sibiha expressed Ukraine’s support for the Syrian people on platform X:
“We express our readiness to pave the way for the restoration of relations in the future and reaffirm our support for the Syrian people,” he wrote.
French president Emmanuel Macron said France wished the Syrian people well:
"The barbaric state has fallen. Finally. I pay tribute to the Syrian people, to their courage, to their patience. In this moment of uncertainty, I wish them peace, freedom and unity," he wrote on platform X.
The EU High Representative for Foreign Affairs Kaja Kallas, like Ukraine, linked the downfall of Assad to his alliance with Russia.
“The end of Assad’s dictatorship is a positive and long-awaited development. It also shows the weakness of Assad’s backers, Russia and Iran,” she said.
“Our priority is to ensure security in the region. I will work with all the constructive partners, in Syria and in the region,” she added.
Russia said it has not taken part in the talks around Assad’s departure.
Its foreign ministry said Russia's military bases in Syria had been put on a state of high alert, but that there was no serious threat to them at the current time. Moscow is in touch with all Syrian opposition groups and urges all sides to refrain from violence.
Iran's foreign ministry called for a national dialogue to form an inclusive government representing all segments of Syrian society.
“Syria's fate is the sole responsibility of the Syrian people and should be pursued without foreign imposition or intervention,” Iran's foreign ministry said.
Iran spent billions of dollars propping up Assad during the Syrian civil war that erupted in 2011 and deployed its Revolutionary Guards to Syria to keep its ally in power so as to maintain Tehran's "Axis of Resistance" to Israel and U.S. influence in the Middle East.
Israeli Prime Minister Benjamin Netanyahu hailed the ousting of Bashar al-Assad on Sunday as a "historic day" that followed the blows delivered by Israel against Assad's supporters Iran and Hezbollah in Lebanon.
On a visit to an observation point in the Israeli-controlled Golan Heights overseeing Syria, Netanyahu said he had ordered Israeli forces to seize areas in the U.N.-monitored buffer zone with Syria to ensure Israel's security.
He said: “If we can establish neighborly relations and peaceful relations with the new forces emerging in Syria, that's our desire. But if we do not, we will do whatever it takes to defend the State of Israel and the border of Israel."
People in Damascus were seen walking inside the Al-Rawda Presidential Palace, with some leaving carrying furniture from inside. The rebels said prisoners had been freed from a large jail on the outskirts of Damascus where the Syrian government detained thousands.
As Syrians expressed joy, Prime Minister Mohammad Ghazi al-Jalali said the country should have free elections so Syrians can choose who they want.
But that would require a smooth transition in a country with complex competing interests, from Islamists to groups with links to the United States, Russia and Turkey.
