Lorries carrying food and other aid have begun entering four besieged areas in Syria for the first time in months, offering hope to tens of thousands of residents.
The Britain-based Syrian Observatory for Human Rights said at least two lorries carrying food baskets and baby formula entered the north-western villages of Foua and Kfarya, which are besieged by insurgents.
Other lorries entered the Damascus suburbs of Madaya and Zabadani, which are besieged by government forces and Lebanese Hezbollah fighters.
Dozens of lorries were supposed to enter the besieged areas, but it was not immediately clear if all would make it in.
Previous planned deliveries have been cancelled at the last minute or halted because of fighting.
The government-controlled Syrian Central Military Media released a video showing a convoy of SUVs from the International Committee of the Red Cross and the Syrian Arab Red Crescent escorting at least two lorries into Madaya.
It gave no further details.
The delivery came a month after the UN humanitarian co-ordinator for Syria appealed to all parties to reach an agreement for immediate access, saying that aid has not reached the areas since November 28.
Some 60,000 people live in the four besieged areas, according to the UN.
Hundreds of thousands of people live in besieged areas around Syria, mainly in areas surrounded by pro-government forces.
The UN embarked on an ambitious plan early in 2016 to establish regular humanitarian access, but it was reportedly stymied by the government as well as an agreement between the warring parties to limit assistance to 60,000 of the most distressed, divided among the four towns.
The flow of aid to the four villages came hours after Physicians for Human Rights issued a report in which it accused the Syrian government of wilfully denying international shipments of food and medicine to many Syrians in besieged areas.
Earlier on Tuesday, a UN investigative commission said it believes government forces deliberately bombed a school complex in the northern countryside in October, killing 21 children, in a scathing report on alleged crimes committed in Syria over the last seven months.
The UN's Independent International Commission of Inquiry on Syria said government forces and their allies had shown a "complete disregard for civilian life and international law" through continued use of cluster munitions, incendiary weapons and chlorine gas.
It also accused an al Qaida-aligned insurgent group fighting on the side of Syria's rebels and a US-backed Kurdish group of conscripting adolescents for combat.
The commission said the attack on the Haas village school complex in the rebel-held province of Idlib on October 26 constituted a war crime.
It said the Syrian air force is the only one known to operate the jets identified in the attack, which was widely reported at the time.
The commission's report also concluded that government forces deliberately targeted the capital's water infrastructure last December, threatening supplies to 5.5 million people.
It said the attack was unjustified, and constituted a war crime.
It did not find any evidence that rebels had poisoned the water supply, as state media alleged.
The Syrian government and its ally Russia maintain they are fighting terrorism.
Meanwhile, a government delegation led by Syria's UN ambassador, Bashar Ja'afari, began meetings with Russian officials in the Kazakh capital Astana.
It is the third summit in Astana running parallel to political talks in Geneva between the government and the opposition.
The Astana talks are centred around cease-fire and humanitarian relief co-ordination, but have brought few results.
Syrian rebels have boycotted this third round, citing the government's continued bombardment of opposition-held areas in Homs and Damascus.
On Monday, activists and the government said a deal had been reached to evacuate rebels and their families from the Homs neighbourhood of al-Waer, ending more than three years of government siege.
Thousands of civilians were expected to depart al-Waer as well, rather than risk conscription or arrest by the Syrian security services.
They will be sent to rebel-held Idlib and other opposition pockets around the country.
The UN condemned a similar agreement that returned the city of Aleppo to government control as a war crime.