At least 112 people died when a powerful bomb hit buses carrying evacuees from besieged Syrian towns, an activists’ group say.
A vehicle filled with explosives hit the bus convoy from government-held towns near Aleppo on Saturday.
The UK-based group the Syrian Observatory for Human Rights said 98 evacuees were killed, along with aid workers and rebel soldiers.
Children were also among the dead, according to several reports.
Many more have been injured and the death toll is expected to rise, the observatory group said.
The explosion shattered coaches and set cars on fire, leaving a trail of bodies, as the convoy waited in rebel territory near Aleppo.
Images from the scene showed bodies lying on the ground outside blackened and devastated vehicles.
In his Easter Sunday address, Pope Francis called the bombing an “ignoble attack on fleeing refugees.”
“May (God) in a particular way sustain the efforts of those who are actively working to bring healing and comfort to the civilian population of Syria, the beloved and martyred Syria, who are victims of a war that does not cease to sow horror and death,” he said.
The bomb went off at Rashidin, west of government-held Aleppo, at about 15:30 local time (12:30 GMT) at the checkpoint where the handover of evacuees was due to take place.
It happened when a vehicle loaded with food arrived and started distributing crisps, attracting many children, before exploding, the BBC’s Middle East correspondent Lina Sinjab said.
She said it was not clear how the vehicle could have reached the area without government permission.
But there is also no evidence that rebels were involved in the attack, as the government claims.
It would not be in the rebels’ interest, our correspondent says, as they were waiting for their own supporters to be evacuated from the other towns.
The planned evacuation was part of the so-called “four towns” deal, where civilians in towns under siege by both sides would be allowed to leave.
It applies to government-controlled Foah and Kefraya, where the bomb struck, as well as rebel-held Madaya and Zabadani near Damascus.
There were fears of revenge attacks on evacuees from rebel-held towns, being moved under a deal.
But the exchange later resumed, with coaches reaching safety on both sides. Evacuations were due to continue on Sunday.
Rebels had earlier accused the government of breaching the terms of the deal, accusing it of trying to bring out more loyalist fighters than agreed, along with civilians.
Foah and Kefraya, most of whose residents are Shia Muslims, have been encircled by rebels and al Qaeda-linked Sunni Muslim jihadists since March 2015.
Madaya and Zabadani, which are predominantly Sunni Muslim, have been besieged since June 2015 by the Syrian army and fighters from Lebanon’s Shia Muslim Hezbollah movement.
A previous attempt at mutual evacuations failed in December when rebels burnt coaches due to be sent to the towns.
Syria war: 112 dead in evacuation bus bombing, observers say}