The United Nations has called for those responsible for bombing a convoy of buses bringing evacuees into Aleppo to answer for their actions.

A suicide bomb blast struck on Saturday (15 April), with the Syrian Observatory for Human Rights (SOHR) stating that at least 112 people were killed in the explosion. The UK-based human rights group reported on the new death toll of Sunday and said the number was expected to rise.

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A spokesperson for the UN Secretary-General said: "The evacuations were being conducted in accordance with the agreement reached pursuant to the Four Towns agreement…

"We call on the parties to ensure the safety and security of those waiting to be evacuated. Those responsible for today's attack must be brought to justice."

Thousands of people were left stranded in two separate convoys on the outskirts of Aleppo for over 30 hours.

People from pro-government areas, such as Foua and Kfraya, were part of a transfer with those from rebel-held areas including Madaya and Zabadani. The deal was brokered by Iran and Qatar, according to Agence France-Presse.

It is believed that the buses were delayed over a dispute between the two sides over how many rebel gunmen could be evacuated.

The convoy was carrying around 5,000 people, including civilians and hundreds of pro-government fighters, Reuters reported.

No group has yet claimed responsibility for the explosion, which targeted pro-government evacuees. However, state media said a "suicide bomber" allegedly used a van meant for carrying aid supplies to enter the area. The SOHR said the explosion came from a vehicle-born improvised explosive device.

"This forced displacement is a clear violation of international humanitarian law and marks yet another sad chapter in the history of this crisis. The absence of the UN and international community from this process has left the civilian populations especially vulnerable, leading to horrific events such as what took place today," the Syrian American Medical Society said in a statement.

"The UN must not abandon its role in protecting innocent civilians and enforcing international humanitarian laws."

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