An official with the UN called for an immediate investigation into the attack, which left more than 80 people injured
At least 28 people in a refugee camp in northern Syria were killed on Thursday despite a ceasefire taking hold in Aleppo, it has been claimed
The deaths occurred when airstrikes struck the Al-Kammouna camp near Sarmada, in Idlib province, the Syrian Observatory for Human Rights said.
The area is controlled by Syria's al Qaeda-linked al Nusra Front.
Observatory chief Rami Abdel Rahman said women and children were among the 28 civilians who were killed.
It is reported that more than 80 people were also injured in the attacks.
Mamun al Khatib, director of the Aleppo-based pro-rebel Shahba Press news agency, claimed the attack had been carried out by Syrian "regime aircraft".
The European Union called the bombings "unacceptable", while an official with the United Nations said there should be an immediate investigation.
On Wednesday, a ceasefire was extended to Aleppo following two weeks of violence in which hundreds had lost their lives.
US Secretary of State John Kerry announced the truce had taken effect on Wednesday night and that violence had already fallen off.
In Aleppo, the Jaish al Islam (Army of Islam) rebel force said the group would respect the truce.
Mediators hope that peace talks backed by the UN could resume later this month in Geneva, although previous rounds have failed to make a major breakthrough.
In central Homs province, another 12 civilians including two women died in a suicide attack and a car bombing on Thursday, the Observatory and state television said.
IS claimed responsibility for the attacks, according to SITE Intelligence Group.
It was not far away from Palmyra, where a Russian orchestra performed a classical music concert in the ancient city's theatre - the scene of IS organised mass executions.