Results are not expected to be announced before tomorrow but a landslide win for Assad over two little-known challengers is not in doubt.
There was no election yesterday in the roughly 60 per cent of the country outside government control, including large areas of second city Aleppo.
And in government-held areas, voters had to brave a rebel bombardment that killed 24 people nationwide on polling day, a monitoring group said.
But state media trumpeted a big turnout which they said prompted polls to be kept open until midnight - five hours later than scheduled.
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It put turnout at 70 per cent in some provinces, although opposition activists were quick to charge that people voted out of fear not conviction.
Assad "thanked all the Syrians who turned out en masse to vote."
His office's Facebook page said Syrians "are proving day after day their belief in a culture of life, hope and defiance, in the face of a culture of death, terrorism and narrow-mindedness."
Three more people died in Damascus as rebels fired 130 mortar rounds into the capital from the suburbs.
The sound of the mortar bombs and government air strikes punctuated voting in the capital throughout the day.
Nine medical workers were killed in an air strike on Zibdin, an opposition-held town near Damascus, the Observatory said.
Washington said it was a "disgrace" to hold a presidential election in the midst of a three-year-old civil war that has killed more than 162,000 people and driven nearly half the population from their homes.