BEIRUT -- Syrian army airstrikes killed at least 70 people, most of them civilians, and wounded scores in attacks Saturday in the northern province of Aleppo that struck civilian areas, including a packed market in a town held by the Islamic State group, activists said.
The deaths occurred in two separate incidents when helicopters dropped explosives-filled barrels. One barrel hit the rebel-held Shaar neighbourhood of the city of Aleppo, killing at least 12 people, most of them from the same family. They included three children and four women, according to the Britain-based Syrian Observatory for Human Rights.
The other attack was far deadlier, hitting a busy market known as Souk al-Hal in the Islamic State-held town of al-Bab in Aleppo's countryside. The Observatory said at least 59 people were killed and dozens wounded, calling it the one of the worst massacres perpetrated by President Bashar Assad's army this year. It said the number of dead likely would rise because many of the wounded were in critical condition.
The Local Coordination Committees reported more than 50 people killed and around 70 wounded in the al-Bab attack. Both groups document violence through a network of activists on the ground in Syria.
Al-Bab is controlled by the Islamic State group, which also confirmed the attack in a statement posted on Twitter. It said 50 people were killed in a "devastating massacre" committed by Syrian army helicopters.
The United Nations Special Envoy for Syria, Staffan de Mistura, strongly condemned the barrel -bomb attacks, in a statement released Sunday. He said such "indiscriminate" aerial attacks were responsible for "the overwhelming majority of the civilian victims in the Syrian conflict."
De Mistura said it is "totally unacceptable that the Syrian air force attacks its own territory in an indiscriminate way, killing its own citizens, as it brutally happened today in Aleppo."
Aleppo, once Syria's commercial hub, has been divided between government and opposition forces since mid-2012, and fighting there has raged since. Government warplanes have dropped explosives-filled barrels on rebel-held neighbourhoods, killing thousands while Syrian rebels have shelled residential areas in government-held parts of the contested city, killing hundreds.
The Syrian military has suffered a series of embarrassing setbacks in northern Syria recently as insurgents captured the city of Idlib and almost all of Idlib province. The Islamic State group has also pushed into central Syria, seizing the ancient city of Palmyra earlier this month after government forces fled the area.
On Saturday, Islamic State militants destroyed the infamous Tadmur prison in Palmyra, publishing pictures that showed fighters carrying plastic containers apparently filled with explosives, and others of the facility being blown up.
The jail that once held thousands of political prisoners lives in the collective memory of Syrians as the place where dissidents were beaten, humiliated and tortured. It held members of the outlawed Muslim Brotherhood which was crushed by Assad's father and predecessor in 1982 as well as many other opponents of the Assad family rule. Blowing up the facility may be part of IS' attempts to gain popularity with the locals -- many of whom suffered from the facility in their midst.
Activists say government forces emptied the prison and moved the prisoners before Palmyra fell to the Islamic State group. The photos were published on an IS-affiliated Facebook page where many of the group's statements have been published.
Also on Saturday, IS militants launched an attack on the predominantly Kurdish city of Hassakeh in northeastern Syria, carrying out two suicide bombings that targeted Syrian troops on the southern outskirts of the city, activists and the group said. The city is split between government troops and Kurdish forces.
Kurdish fighters have made significant advances against IS militants in Hassakeh province in recent days. Saturday's surprise attack appeared to be an attempt to make up for those losses.
State-run news agency SANA reported that life in the city was "normal and all government institutions functioning as usual" despite shelling by IS militants that struck civilian homes and the city's downtown area earlier Saturday.
More than 220,000 people have been killed in Syria since the start of the uprising against Assad in March 2011.
