This story has been updated.

UPDATE, 10:28 a.m. EDT: The number of people killed in Syria's northern Aleppo province by barrel bombs dropped from government helicopterst has risen to at least 71, according to the U.K.-based Syrian Observatory for Human Rights. The organization reports 59 people died in the strike on al-Bab - a town currently held by Islamic State group militants and 12 others were killed in the city of Aleppo.

Original story below.

At least 45 civilians were killed in two separate attacks by pro-government forces in Syria on Saturday, the U.K.-based Syrian Observatory for Human Rights said. The deaths occurred when helicopters allegedly dropped barrel bombs on the Shaar neighborhood of the city of Aleppo and on the town of Al-Bab, located about 25 miles northeast of Aleppo city.

“Twelve civilians were killed, including 3 children, 4 women, and 8 from one family … by an explosive barrel [that] fell near a car carrying a family in al-Sha’ar neighborhood,” the Observatory said in the statement. “Thirty-three civilians were killed while dozens others were wounded by an explosive barrel target Souq al-Hal area in Al-Bab city.”

Rami Abdel Rahman, the founder and head of the Observatory, said the death toll is likely to rise as many of those injured are believed to be in critical condition. “People often gather on Saturday mornings at the Al-Hail market in Al-Bab, which is why the number of dead was so high,” he told Agence-France Presse.

Al-Bab is controlled by militants of the Islamic State group, while the Shaar neighborhood is under other rebel groups fighting Syrian President Bashar Assad’s government.

The Syrian government has, in the past, been criticized for its indiscriminate use of barrel bombs, which are improvised explosive devices made using oil drums, gas cylinders or water tanks packed with explosives and scrap metal. Assad, however, has denied that his forces use, or even possess, such bombs.

“I know about the army. They use bullets, missiles and bombs. I haven't heard of the army using barrels, or maybe, cooking pots,” Assad told a BBC journalist in February, who described the response as “flippant.”

Saturday’s attacks come just a day after rebels, belonging to a Syrian coalition known as the Jaysh al-Fatah, seized Ariha -- the last government-controlled town in the country’s northwestern province of Idlib -- forcing pro-regime soldiers to retreat to its outskirts.