BEIRUT - A rare UN-backed deal between Syria's warring sides saw hundreds of fighters and civilians evacuate three towns on Monday, as bomb blasts in the regime-held city of Homs killed at least 32 people and wounded 90 others.

Syria's state news agency SANA reported two car bomb blasts, but gave a lower initial toll of six dead and 37 wounded. It was the second major attack in the city since a ceasefire deal took effect earlier this month, paving the way for the government to take over the last rebel-controlled area of Homs.

President Bashar al-Assad's regime has agreed to several ceasefires with rebel groups in the past but Monday's evacuation plan was one of the most elaborate in the nearly five-year war.

The United Nations has been pushing for such local deals as global powers pursue wider efforts to resolve a conflict that left more than 250,000 dead and forced millions from their homes.

More than 450 fighters and civilians, including the wounded, began leaving three flashpoint areas in Syria as part of a six-month truce reached in September.

At least 120 people, including rebels and some civilians, crossed from the last rebel bastion on the Syrian border into Lebanese territory on Monday, an AFP journalist at the scene said.

The Zabadani residents were to fly from Beirut to Turkey, before travelling back into opposition-held areas in Syria, said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.

Another 335 people, also including civilians, travelled from two regime-controlled villages in northwestern Syria into Turkey on Monday, Abdel Rahman said. Residents of the mainly Shiite villages of Fuaa and Kafraya crossed through the Bab al-Hawa border point and are to fly into Beirut to travel overland to Damascus.

According to a source close to the negotiations, national flag carrier Turkish Airlines will fly both sets of evacuees.

"We appreciate the cooperation of all sides, of the Syrian, Turkish, and Lebanese governments, and all the sides that have signed on to this humanitarian agreement," said UN humanitarian coordinator Yaacoub El Hillo in comments to Al-Mayadeen TV from the Syrian side of the border with Lebanon.

It is the first time the neighbouring countries are involved in such an evacuation deal.

The next part of the deal, according to the Britain-based Observatory, would see humanitarian aid delivered into the towns.

The Observatory's Abdel Rahman said Assad's regime was keen to reach such agreements as part of its "efforts to secure the capital by seizing control of rebel-held areas or through ceasefire deals".

Al-Manar, a Lebanese television station affiliated with pro-Assad Shiite group Hezbollah, broadcast live footage of the Zabadani convoy entering Lebanon.

Dozens of people gathered at the Masnaa crossing rushed the buses as ambulance sirens wailed.

The station had provided coverage earlier of bearded fighters wearing military-style fatigues boarding the buses amid bombed-out ruins in Zabadani.

Similar ceasefire deals have been implemented in other parts of the country throughout Syria's war, often after crippling sieges of rebel-held areas.

Government figures and local leaders reached a deal last week to evacuate thousands of jihadists and civilians from southern Damascus, but the agreement was apparently derailed after the death of rebel chief Zahran Alloush on Friday.

Alloush, the head of Jaish al-Islam, the foremost rebel group in Damascus province, was killed in an air strike claimed by Syria's government.

In one of the most significant such deals so far, anti-government rebels earlier this month quit the last opposition-held district of the central city of Homs, once dubbed "the capital of the revolution." But violence has since rocked the city.

On Monday, at least 19 people were killed and dozens wounded in large bomb blasts in the city's Al-Zahraa neighbourhood, Syria's state news agency SANA said.

State television said two explosions caused by car bombs and a blast caused by a suicide attacker wearing an explosives-laden belt hit Al-Zahraa's main square.

The station broadcast scenes of chaos in the central city, as firetrucks tried to extinguish flaming cars and rescue workers carried bloodied victims. The residents of Al-Zahraa are mostly Alawites, the minority sect of Syria's ruling clan.

"These terrorist, cowardly, and desperate attacks come in response to the growing spirit of national reconciliation throughout Syria," Prime Minister Wael al-Halqi said in comments carried by state news agency SANA.

The Observatory confirmed the blasts and reported at least 32 dead. The attack came less than three weeks after the Islamic State jihadist group claimed explosions in the same neighbourhood that left 16 people dead.

Elsewhere in Syria, at least 11 people were killed and 40 wounded in rebel shelling of a government-controlled neighbourhood in the northern city of Aleppo, state TV reported.