BEIRUT - Syrian regime helicopters on Monday dropped barrel bombs on opposition-held districts in the northern city of Aleppo, killing at least 31 people including several children, an NGO said.

The Syrian Observatory for Human Rights said a number of people were injured, some seriously, in the attacks on the Sukkari and Ashrafiyeh neighbourhoods and that the number of dead was expected to rise.

The monitoring group distributed gruesome images from the scene of the attacks on Sukkari, where 25 people were killed, showing residents holding body parts of victims from the raid. Observatory director Rami Abdel Rahman said a first attack created chaos, with residents and medics rushing to the scene to help. Several minutes after the first attack, a second bomb hit the same site, with those present trying to flee but many failing to do so in time.

Another six people died in a separate barrel bomb attack in a rebel-held area of the Ashrafiyeh neighbourhood, in the north of the city.

Syria’s regime has waged a fierce aerial offensive against rebel-held parts of Aleppo since last December.

The Observatory said in May 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 an aiming mechanism, causing indiscriminate casualties.

Tens of thousands of people have fled Aleppo’s opposition districts because of the aerial campaign.

Meanwhile, a week after Syria announced a wide-ranging amnesty, state media, a newspaper close to the government, and activists have offered wildly contradictory figures on the number of prisoners freed.

Activists said they could confirm the release of only several dozen prisoners and were sceptical of other numbers being bandied about. Activist groups that monitor the situation of political prisoners in Syria do not yet have full lists of names of the released, sparking concern about the transparency of the process.

There are also contradictions between the figures published by state news agency SANA, which put the number at 1,200 freed, and Al-Watan, a newspaper close to the government, which said Monday that some 10,000 detainees had been released.

The Syrian Observatory for Human Rights, a Britain-based monitoring group, also gave a different number, saying 2,700 prisoners had been released across Syria.

Al-Watan said among the 10,000 freed were 4,500 accused under the country’s controversial “terrorism” law, which has seen tens of thousands of peaceful and armed opponents jailed.

The newspaper quoted the chief prosecutor at the country’s terrorism court as saying “the process of releasing detainees will continue throughout the month”.

And the daily predicted that the number of those freed could rise to 30,000 prisoners, noting that some 150,000 people are currently in jails in Syria.

According to the Observatory, 100,000 people have been arrested by the government since the beginning of the 2011 uprising against President Bashar al-Assad’s regime.

Among those are 18,000 people whose whereabouts are currently unknown.

Human rights activists have described dire conditions in jails and security facilities used to hold prisoners in Syria, with mistreatment common.

The amnesty announced last week is the first that has extended to those facing charges under the country’s anti-terrorism legislation, which has been used against peaceful activists among others.

Though the amnesty should apply to tens of thousands of people, activists said that only a few hundred had been freed so far and prominent figures including journalist Mazen Darwish remained in jail.

Last week, Raneem Maatuq, the daughter of a prominent rights lawyer who has also been jailed, was freed, though there was no word on the release of her father.

Also freed was Jalal Nawfal, a doctor and leftist opposed to Assad’s regime who had been jailed since early 2014 for his dissident activities.