Syrian government helicopters dropped barrel bombs on opposition-held districts of the northern city of Aleppo on Monday, killing at least 31 people including several children, AFP reports.
Some of the wounded were in a serious condition after the strikes on the Sukkari and Ashrafiyeh neighborhoods, the Syrian Observatory for Human Rights told the news agency.
Two bombs hit Sukkari minutes apart, with the second catching helpers who had gone to the assistance of the casualties from the first.
"We were sleeping safely when the first barrel dropped around midnight," said resident Abu Mohammad, according to AFP.
He added, "And when people came to the rescue, a second barrel dropped, so all those people who were on the site were dead. We don't have military bases in our area. All people here are civilians. Why is he (President Bashar Al-Assad) attacking us?"
Using barrel bombs against rebel-held areas of Aleppo has become a common occurrence, as the regime has used this method to attack rebels for months.
The Observatory said in May that the campaign had killed nearly 2,000 people -- more than a quarter of them children -- since the beginning of 2014.
Rights groups have decried the regime's use of barrel bombs as unlawful because they lack any guidance mechanism, causing indiscriminate casualties.
Tens of thousands of people have fled rebel-held districts of Aleppo in the face of the bombing.
In January, the UN Security Council had been working on a statement that would have expressed outrage at the use of missiles and barrel bombs by Assad’s forces, but Russia vetoed the initiative.