The Syrian Observatory for Human Rights say at least 126 people were killed, including 68 children, in a suicide bomb attack on bus convoy near Aleppo Saturday.

The United Nations has demanded that those responsible for the bombing be brought to justice.

On Saturday a suicide car bomber targeted stranded buses holding thousands of evacuees on a road near Aleppo.

UN Secretary General Antonio Guterres condemned the attack and called on all parties "to ensure the safety and security of those waiting to be evacuated."

The blast came as thousands of people were left stranded in two separate convoys on the edge of Aleppo city for more than 30 hours.

Residents from pro-government areas including Foua and Kfraya were involved in a "transfer" with those from rebel held areas like Madaya and Zabadani.

The buses had been held up by a disagreement between the two sides about how many rebel gunmen could be evacuated.

Hours after the explosions the transfers resumed, with more than 100 buses from both sides arriving at their destinations.

Nobody has yet claimed responsibility for the blast, which targeted pro-government evacuees, but the two sides have both blamed each other.