Rebels started withdrawing from the heart of the Syrian city of Homs on Wednesday, leaving an early center of the revolt against the Syrian government and handing President Bashar al-Assad a symbolic victory less than a month before his likely re-election.

Activists said two buses carrying the first of many hundreds of fighters left the besieged city center, heading for rebel-held areas of northern Homs province - an evacuation arranged under a deal between insurgents and Syrian government forces.

The rebels had held out in the Old City district and several other areas despite being undersupplied, outgunned and subjected to more than a year of siege.

Their evacuation comes after months of gains by Syrian government forces, backed by Lebanese militant ally Hezbollah.

The final withdrawal of rebels from the center of the city, where protests first erupted against Assad in 2011, would consolidate his military control ahead of a June 3 presidential election.

Assad is widely expected to win the vote, which his opponents have dismissed as a charade. They say no credible election can be held in a country fractured by an ongoing civil war, with swathes of territory outside government control, 6 million people displaced and another 2.5 million refugees abroad.

The Homs evacuation is part of a deal between Syrian government forces and rebel fighters under which the overwhelmingly Sunni Muslim rebels also agreed to ease their siege of two northern Shiite towns, Nubl and al-Zahraa.

The deal, which was negotiated with the assistance of Iran's ambassador to Syria, will be guaranteed by the United Nations and Iran, according to a copy of the text seen by AFP.

The Syrian Observatory for Human Rights said rebels opened the roads to allow aid into the two towns on Wednesday morning at the same time as the first buses collected the departing rebel fighters from Homs.

A total of 1,200 fighters are expected to leave Homs in stages, carefully synchronized with the aid delivery and the release of several captives held by the rebels near Nubl and Zahraa.

Provincial governor Talal Barazi was quoted by state news agency SANA as saying Wednesday's operation would clear Homs of gunmen and weapons, and would be applied across the whole of Homs city.

As well as their stronghold in the Old City neighborhoods, rebels also still have a presence in the Al-Waer suburb on the city's northwestern outskirts.

More than 150,000 people have died in Syria's civil war.

Millions more have fled their homes and the government has lost control of swathes of territory across the north and east. Fighting regularly kills more than 200 people a day.

Reuters-AFP