Syrian rebels on Wednesday managed to bring food into eastern Aleppo for the first time since government forces isolated the opposition enclave last month, a monitoring group said.
The United Nations meanwhile said an announcement by government ally Russia of three-hour humanitarian pauses over three days to allow aid into Aleppo was inadequate.
Vehicles loaded with food entered through a breach rebels had made four days earlier in government lines on the city's south-western perimeter, the Syrian Observatory for Human Rights said.
The rebels had built up earth barriers around the route, enabling them to secure the convoy even though government forces had on Tuesday won back ground and advanced to firing positions over it, the Observatory reported.
"Tomatoes are here after one month of absence," Aleppo-based activist Yassin Abu Raed posted on his Facebook page, along with pictures of small trucks carrying mainly fresh vegetables.
Later Wednesday, Russian General Sergei Rudskoi told reporters that all military hostilities in Aleppo province would halt for three hours on three days starting Thursday to allow humanitarian convoys to deliver aid to civilians.
"As of tomorrow, humanitarian 'windows' will open from 10 am to 1 pm local time to guarantee the safe passage of convoys into Aleppo," Rudskoi said in comments carried by state news agency TASS.
"All military hostilities, flights and artillery strikes should stop during that time."
But the UN's top aid official quickly poured cold water on Rudskoi's announcement, saying a three-hour pause daily would not be enough to deliver sufficient aid.
"What could be achieved in that three hours?" UN humanitarian affairs chief Stephen O'Brien asked.
"Is it to meet the need, or would it only just meet a very small part of the need? Clearly, from out point of view, we're simply there to meet the need - all the need," he added.
O'Brien repeated a previous UN call for pauses of at least 48 hours, saying that much time would be needed for aid to be loaded onto trucks and delivered to the city and for evacuations to take place.
Amid ongoing fighting in the city, state news agency SANA said 13 people had been killed in rebel shelling on the Hamdaniyeh district close to the rebel breakthrough point.
The observatory said eight people had been killed in shelling on residential areas in the district, including at least five civilians.
Last month government forces captured the last remaining rebel supply route into the east, Castello Road, raising fears that some 250,000 to 300,000 civilians there would come under siege.
The United Nations previously warned that food supplies in eastern Aleppo were likely to run out by mid-August.
In the countryside outside Aleppo, meanwhile, at least five people were killed and dozens were injured when airstrikes hit a medical center in the rebel-held village of Aroum al-Kubra, the observatory said.
"There was a nursing training session in the centre. Some of the people who were inside were killed and others outside," Abdel Rahman of the White Helmets, a non-governmental emergency group operating in rebel-held areas, told dpa.
Activists in the area said the planes were believed to be Russian. Rights groups and analysts have previously accused Russia and the Syrian government of deliberately targeting hospitals in rebel-held areas.
In May, the UN Security Council passed a resolution demanding protection of hospitals in conflict zones, days after at least 30 people were killed in an airstrike on a hospital in eastern Aleppo.