DAMASCUS (AFP) - Mr Bashar al-Assad has been re-elected Syria's president with 88.7 per cent of the vote in an election labelled a farce by rebels fighting to overthrow him, and whose outcome was never in doubt.

The other candidates in Tuesday's vote - Mr Hassan al-Nuri and Mr Maher al-Hajjar - won 4.3 per cent and 3.2 per cent, respectively, parliamentary speaker Mohammad al-Lahham said.

"Congratulations to the Syrian people for its choice and decision," he said. "Syria has its leader and its captain, who will lead the ship to the shore of safety and security."

But rebel spokesman Omar Abu Leyla in the eastern province of Deir Ezzor said "the Syrian people has made its decision, and will continue in its revolution, whatever the cost".

"After three years, it is impossible to go back, until we get our demands, which were freedom and justice," he told AFP via the Internet.

Meanwhile, activist Raed from northern Syria posted on his Facebook page the central slogan of the Arab Spring that inspired a revolt in March 2011 against Mr Assad: "The people want the fall of the regime."

Minutes after the announcement, people took to the streets in Damascus to celebrate. Many chanted, some with the Syrian flag wrapped around their shoulders.

"Long live Assad's Syria! God protect our leader Bashar al-Assad!" they chanted.

"God, Syria, Bashar and that's it!" they cried, carrying portraits of Mr Assad and flags.

Celebratory shots fired by Assad supporters killed at least three people in the capital and wounded dozens more, the Syrian Observatory for Human Rights said.

In Aleppo in the north of Syria, which is divided into rebel and regime-held sectors, another 20 people were wounded in celebratory gunfire, while the air force carried out fresh barrel bomb attacks on opposition areas in the city.

The election was held only in the roughly 40 per cent of Syrian territory controlled by the regime, and among some 200,000 expatriates.

An official said turnout reached 73.42 per cent, or 11.6 million people out of 15.8 million called on to vote.

However, opposition activists were quick to claim people had voted out of fear, not conviction.

Earlier, Mr 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".

The US said it was a "disgrace" to hold an election, in the midst of a three-year-old war that has killed more than 162,000 people and driven nearly half the population from their homes.

The war broke out after Mr Assad's regime unleashed a brutal crackdown on a peaceful revolt demanding change, that later morphed into an armed uprising.

Secretary of State John Kerry, who was in Beirut on Wednesday, described the vote as a "great big zero", and urged Assad allies Iran, Russia and Lebanon's Shi'ite movement Hizbollah to end the war.

With millions having fled their homes and the country, Mr Kerry announced US$290 million (S$364.8 million) in humanitarian aid for Syria and countries hosting refugees.

"The conflict is the same, the terror is the same, the killing is the same."

But opposition activists have criticised Washington for failing to take decisive action over the conflict, despite its repeated calls for Mr Assad to step down.

"Thank you free world for blessing a serial killer who is going to kill and displace the rest of Syrians and destroy what is left of Syria," read a post on an activists' campaign page decrying the vote as a "blood election".

Meanwhile, Assad ally Moscow, which welcomed the election as a step towards a political solution, called for the speedy appointment of a new UN envoy.

Mr Lakhdar Brahimi, who brokered two rounds of abortive peace talks between Damascus and the opposition this year, stepped down on Saturday saying his mediation had reached a stalemate.

He had infuriated Damascus by criticising Tuesday's election as an obstacle to his peace efforts.

Russia's UN envoy Vitaly Churkin, who has just taken over the Security Council's chairmanship, said it would be "fundamentally flawed" to ignore the need for a quick successor to Mr Brahimi to relaunch peace efforts.

Moscow, which sent observers to monitor the election, has infuriated the West by four times vetoing draft Security Council resolutions in defence of its Damascus ally, including a bid to refer Syria to the International Criminal Court.

For his part, Human Rights Watch chief Kenneth Roth tweeted: "Syria scrapes bottom in quest for legitimacy pulling in election observers from N(orth) Korea, Iran, Russia and Zimbabwe."