(CNN) A UN-established commission has issued a damning report on human rights violations in Syria's war-ravaged Aleppo , accusing both sides to the conflict of committing war crimes.

The commission gathered evidence to confirm witness accounts that the Syrian and Russian governments used prohibited cluster munitions on civilians in rebel-held eastern Aleppo, suggesting the deliberate destruction of hospitals with repeated airstrikes, among other rights violations.

Cluster munitions release smaller "bomblets" that cover a wider area than regular bombs, and are criticized for causing damage beyond intended targets.

CNN has reached out to Russian officials and the Syrian mission to the UN for a response to the report, but they have not yet replied. Both countries have in the past denied deliberately targeting hospitals and schools, as well as the use of cluster bombs.

The commission could not always distinguish whether it was Syrian or Russian planes carrying out particular airstrikes.

Rebel fighters take aim at pro-government positions in Aleppo on Friday, December 9.

Rebel fighters take aim at pro-government positions in Aleppo on Friday, December 9.

Civilians from eastern Aleppo stream into a government checkpoint at the al-Hawoz street roundabout on Saturday, December 10.

Civilians from eastern Aleppo stream into a government checkpoint at the al-Hawoz street roundabout on Saturday, December 10.

In this handout photo from the International Committee for the Red Cross, women displaced from eastern Aleppo gather at a shelter in the village of Jibreen, south of Aleppo, on December 12.

In this handout photo from the International Committee for the Red Cross, women displaced from eastern Aleppo gather at a shelter in the village of Jibreen, south of Aleppo, on December 12.

Pro-government forces patrol Aleppo's Sheikh Saeed district on December 12 after it was recaptured from rebel forces.

Pro-government forces patrol Aleppo's Sheikh Saeed district on December 12 after it was recaptured from rebel forces.

A woman reacts as she evacuates the Bustan al-Qasr neighborhood with her two children on December 13.

A woman reacts as she evacuates the Bustan al-Qasr neighborhood with her two children on December 13.

Pro-government fighters wave from a truck as they pass civilians fleeing the Bustan al-Qasr neighborhood on December 13.

Pro-government fighters wave from a truck as they pass civilians fleeing the Bustan al-Qasr neighborhood on December 13.

Syrian civilians take food from a storage room that was formerly held by the opposition forces in eastern Aleppo's al-Kalasseh neighborhood on December 13.

Syrian civilians take food from a storage room that was formerly held by the opposition forces in eastern Aleppo's al-Kalasseh neighborhood on December 13.

A Syrian child cooks in the street in a rebel-held area of Aleppo on December 13.

A Syrian child cooks in the street in a rebel-held area of Aleppo on December 13.

Syrian residents, fleeing violence in the Bustan al-Qasr neighborhood, arrive in Aleppo's Fardos neighborhood on December 13.

Syrian residents, fleeing violence in the Bustan al-Qasr neighborhood, arrive in Aleppo's Fardos neighborhood on December 13.

Pro-government forces walk in the ancient Umayyad Mosque after capturing the area on Tuesday, December 13.

Pro-government forces walk in the ancient Umayyad Mosque after capturing the area on Tuesday, December 13.

A wounded woman is helped into the bed of a truck on December 14.

A wounded woman is helped into the bed of a truck on December 14.

A member of the civil defense carries a wounded boy out of a hospital in eastern Aleppo on December 15.

A member of the civil defense carries a wounded boy out of a hospital in eastern Aleppo on December 15.

A woman in a wheelchair waits to board a bus during evacuations on December 15.

A woman in a wheelchair waits to board a bus during evacuations on December 15.

Buses line up to transport people away from eastern Aleppo on December 15.

Buses line up to transport people away from eastern Aleppo on December 15.

Staff members of the Syrian Red Crescent wait near ambulances as the evacuation operation gets underway on December 15.

Staff members of the Syrian Red Crescent wait near ambulances as the evacuation operation gets underway on December 15.

A wounded boy sits inside an ambulance during the evacuations on December 15.

A wounded boy sits inside an ambulance during the evacuations on December 15.

Civilians arrive in the opposition-controlled Khan al-Aassal region, to the west of Aleppo, on Thursday, December 15. Most of the civilians from Aleppo will be taken to a rebel-controlled area in the neighboring province of Idlib.

Civilians arrive in the opposition-controlled Khan al-Aassal region, to the west of Aleppo, on Thursday, December 15. Most of the civilians from Aleppo will be taken to a rebel-controlled area in the neighboring province of Idlib.

Pro-government forces guard a convoy of buses and ambulances during the evacuation operation on December 16.

Pro-government forces guard a convoy of buses and ambulances during the evacuation operation on December 16.

Russian soldiers and Syrian pro-government forces look on as civilians and rebel fighters are evacuated from Aleppo on Friday, December 16. Evacuations began a day earlier under a new ceasefire between rebels and pro-government forces.

Russian soldiers and Syrian pro-government forces look on as civilians and rebel fighters are evacuated from Aleppo on Friday, December 16. Evacuations began a day earlier under a new ceasefire between rebels and pro-government forces.

Buses drive through the Syrian government-controlled crossing of Ramoussa, on the southern outskirts of Aleppo, on December 18.

Buses drive through the Syrian government-controlled crossing of Ramoussa, on the southern outskirts of Aleppo, on December 18.

Militants burned at least five buses assigned to evacuate people in Aleppo on Sunday, December 18. Aleppo has been held by rebels for the past four years, but it is now almost entirely under government control.

Militants burned at least five buses assigned to evacuate people in Aleppo on Sunday, December 18. Aleppo has been held by rebels for the past four years, but it is now almost entirely under government control.

Syrian pro-government forces wave to evacuees from the villages of Foua and Kefraya on December 19. While people were being bused out of Aleppo, safe passage was also given to people in areas held or besieged by rebels, the Aleppo Media Center activist group said.

Syrian pro-government forces wave to evacuees from the villages of Foua and Kefraya on December 19. While people were being bused out of Aleppo, safe passage was also given to people in areas held or besieged by rebels, the Aleppo Media Center activist group said.

Civilians wait to be bussed out of besieged areas of eastern Aleppo, Syria, as evacuations continue on Monday, December 19. A people-swap deal struck between rebels and Syrian government forces was set to begin over the weekend, but evacuations were temporarily put on hold after a number of buses were set on fire.

Civilians wait to be bussed out of besieged areas of eastern Aleppo, Syria, as evacuations continue on Monday, December 19. A people-swap deal struck between rebels and Syrian government forces was set to begin over the weekend, but evacuations were temporarily put on hold after a number of buses were set on fire.

The report also said Syrian forces carried out a deadly aid convoy attack in September 2016, giving a harrowing account of how machine guns were fired from aircraft at those who had survived rounds of bombings.

The commission heard more witness testimony of chemical attacks using chlorine gas , saying the evidence pointed to the Syrian regime being behind them. The report said the use of chlorine in attacks was a war crime and showed "a blatant disregard for international legal obligations."

But the commission said it found no evidence that Russia had used chemical weapons.

Both Syria and Russia have denied using chemical weapons.

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"On both sides of the city, civilians paid the highest price for the brutality of violence that assailed Aleppo. In eastern Aleppo, pro-government forces pummeled vital civilian infrastructure, with disastrous consequences. Day after day, hospitals, markets, water stations, schools and residential buildings were razed to the ground," the report said.

It added that civilians in turn avoided hospitals, including pregnant women, "who increasingly gave birth at home without medical assistance or opted for caesareans to avoid hours in labor in hospital."

"In western Aleppo, civilians lived in fear of indiscriminate and deliberate shelling by armed groups," the report said, calling such shelling a war crime.

A man rescues a wounded child after an airstrike in Aleppo on November 18, 2016.

'Surrender or starve' siege

The eastern Aleppo enclave had been held by rebel groups for four years when Syrian forces besieged it in July 2016. The commission documented rights violations between this period and late December, when the regime regained control of the area.

The retaking of Aleppo was seen as a major turning point in the war, which has raged for nearly six years.

The government kept a tight grip on the area over those six months, as it and its most powerful ally, Russia, carried out airstrikes over the enclave, reducing much of it to rubble.

The siege cut civilians and armed groups off from much-needed food and aid supplies, a common tactic employed by the regime of Syrian President Bashar al-Assad.

"Resorting to a concerted aerial campaign coupled with ground forces that encircled eastern Aleppo city, government forces and their allies employed brutal tactics to force the armed groups to surrender," the report said.

The report found that the evacuations of eastern Aleppo constitue a war crime.

"The siege simultaneously deprived civilians of freedom of movement and prevented basic commodities, including food and medical supplies, from entering the city.

"Widely used throughout the conflict, the use of this 'surrender or starve' tactic by the pro-government forces has proven disastrous for civilians but successful for overtaking opposition-held territory."

Machine guns fired in aid convoy attack

The report is one of the most comprehensive official accounts of rights abuses in Aleppo to date.

It also gives the most detailed description of the attack on the UN-led aid convoy on September 19 last year. It said that evidence from the site pointed to the Syrian regime being behind the attack. Russia and Syria both denied carrying out the attack at the time.

The attack, which the report said killed at least 14 civilian aid workers and injured 15 others, led to the suspension of aid deliveries for months.

It destroyed 17 trucks, and with them food, medicine, children's clothes and other supplies destined for families in western Aleppo areas controlled by armed groups, the report said.

Through accounts from survivors and others in the vicinity of the attack at an aid warehouse, the commission found that helicopters first dropped barrel bombs on the site, striking the warehouse and a family home nearby.

Much of eastern Aleppo has been reduced to rubble from Russian and Syrian airstrikes.

As people rushed to the scene to assist the wounded, they were forced to retreat and seek cover when the helicopters returned and dropped a second round of barrel bombs, before machine guns were fired from the aircraft in their direction.

Survivors described scenes of panic as workers were killed and maimed in the dark in the attack that lasted 30 minutes, the commission found.

The commission also found that the evacuations of civilians form eastern Aleppo in November and December -- under a complex people-swap deal that moved civilians and fighters to other areas -- constituted a war crime because the agreement was made for strategic reasons, and not for the security of civilians, and it amounted to forced displacement.

Stop weapons sales, commissions says

The commission recommended that the international community support the establishment of a body to investigate war crimes and rights violations in Syria since March 2011, in accordance with a UN resolution.

It also asked countries to curb the supply of weapons to warring parties, "particularly cluster munitions and incendiary weapons, which are indiscriminate when used in civilian-inhabited areas and pose a threat to civilians for years after the cessation of hostilities."