At Least 43 Killed as Explosion Hits Buses Evacuating People in Syria's Foua, Kfraya

Rashidin (Syria): A suicide car bomb attack on buses carrying Syrians evacuated from two besieged government-held towns killed 43 people on Saturday, as US-backed fighters advanced in their push towards the Islamic State group's Raqa stronghold.

The Syrian Observatory for Human Rights said the blast targeted buses carrying residents evacuated from the northern towns of Fuaa and Kafraya under a deal reached between the regime and rebels.

Bodies were still being recovered from the attack at a transit point in Rashidin, west of Aleppo, according to the Observatory.

"The suicide bomber was driving a van supposedly carrying aid supplies and detonated near the buses," the monitoring group said.

AFP's reporter in rebel-held Rashidin saw several bodies, body parts and blood scattered on the ground.

The bombing took place as thousands of evacuees from Fuaa and Kafraya waited to continue their journey to regime-controlled Aleppo, the coastal province of Latakia, or Damascus.

More than 5,000 people who had lived under crippling siege for more than two years left the two towns, along with 2,200 evacuated from rebel-held Madaya and Zabadani, on Friday.

It has sucked in regional and international powers and allowed jihadist groups to seize vast areas of the country.

US-backed fighters reached the outskirts of a key jihadist-held town in northern Syria on Saturday as part of an offensive aimed at the IS bastion of Raqa.

The Syrian Democratic Forces (SDF), an Arab-Kurdish alliance supported by US-led coalition air strikes and special forces advisers, surrounded Tabqa in early April and have cut its main supply routes.

The town and a vast nearby dam are considered key prizes in the broader offensive for Raqa, the de facto Syrian capital of IS's self-proclaimed "caliphate", about 55 kilometres to the east.

SDF fighters are within a few hundred metres (yards) of Tabqa, said Observatory head Rami Abdel Rahman. He said heavy clashes were under way around the two suburbs as IS attempted to counter-attack.

The SDF launched its campaign for Raqa in November and has since captured most of the surrounding province. It has been backed by US-led coalition air strikes, along with advisers and even an American Marines artillery battery. Raqa was home to around 240,000 residents before 2011 and more than 80,000 people have fled to the city from other parts of the country since the start of Syria's civil war.

Tabqa sits on a key supply route into Raqa and served as an important IS command base, housing the group's main prison. Backed by Russia and local militias, pro-government forces have made a string of recent gains.

The government and rebels have brokered a series of deals to evacuate people from besieged areas, which Damascus touts as the best way to end the violence. Rebels say they are forced out by siege and bombardment.