Bashar al-Assad has been sworn in for a third seven-year term as president of Syria, after an election last month that opponents dismissed as a "farce".
State television broadcast what it said was a live ceremony from the presidential palace in Damascus.
Mr Assad vowed to fight "terrorism" until security was restored to all of the country, but also promised to offer "national reconciliation" to opponents.
He has defied calls to step down since an uprising began in March 2011.
The conflict that erupted after the authorities launched a brutal crackdown on protests has left at least 170,000 people dead and driven more than nine million others from their homes.
Mr Assad won 88.7% of the votes cast in the first multi-candidate election in decades, which took place only in areas of Syria that were under government control.
After taking the oath of office on Wednesday, Mr Assad told his supporters: "Syrians, three years and four months... have passed since some cried 'freedom'."
"They wanted a revolution, but you have been the real revolutionaries. I congratulate you for your revolution and for your victory," he added.
"Those who lost their way can now see clearly... the monstrous faces have been unveiled, the mask of freedom and the revolution has fallen."
Mr Assad also promised that Arab, regional and Western countries who are helping the rebels trying to topple him would soon "pay a high price for supporting terrorism".
Over the past year, Mr Assad's forces - backed by Iran and the Lebanese Shia Islamist movement Hezbollah - have consolidated their control over a corridor of territory stretching north from the capital to the city of Homs and then into Hama and Latakia provinces.
However, large swathes of the north and east remain under the control of rebel forces, including the Islamic State in Iraq and the Levant (Isis).
The powerful al-Qaeda breakaway declared the creation of a "caliphate" in its territories last month after launching an offensive that saw it capture parts of northern and western Iraq.
Western-backed and more moderate Islamist rebels in Syria, who have been engaged in deadly battles with the group's fighters since the start of the year, rejected the announcement.