In a triumphant speech on Wednesday delivered after he took the oath of office at a red carpet ceremony in Damascus, Assad branded the 2011 Arab uprisings a "fake spring".

Assad, 48, won a June election as it was staged more than three years into a devastating war that has killed more than 170,000 people and uprooted millions.

"Syrians, three years and four months... have passed since some cried 'freedom'," Assad declared, referring to the 2011 revolt.

"They wanted a revolution, but you have been the real revolutionaries. I congratulate you for your revolution and for your victory," Assad told his supporters.

"Those who lost their way can now see clearly... the monstrous faces have been unveiled, the mask of freedom and the revolution has fallen."

Assad's inauguration comes with much of the world's attention focused elsewhere, as violence engulfs Iraq and Gaza even though his troops continue to pound militant-held areas of second city Aleppo.

During the first two years of the Syrian insurgency, which began as a peaceful protest movement before transforming into an armed rebellion, the opposition's Western and Arab supporters repeatedly insisted he must step down.

But the rise of the so-called Islamic State (IS) has turned the tide and raised fears about the future.

Assad has repeatedly branded the insurgency as a foreign-backed "terrorist plot".

More than 1,000 people were invited to Wednesday's inauguration, with Assad arriving at the presidential palace in a black sedan car before being met on the red carpet by a military band.

Parliamentarians and other guests cheered for Assad in the hall where he spoke.

Assad won the June 3 election held only in government-controlled territories by 88.7 percent, defeating two other candidates.

HH/HH