Convoys have reached two out of Syria's 19 besieged areas on the day of the deadline set by the international community over the arrival of humanitarian aid to affected populations.
The first Red Cross convoy entered the rebel-held Syrian town of Daraya on Wednesday, in the first such delivery since a government-imposed siege began in 2012.
Both UN and Syrian Arab Red Crescent staff were involved in the delivery, the International Committee of the Red Cross said.
Al Jazeera's diplomatic editor James Bays, reporting from the UN headquarters in New York, said the Daraya convoy carried some medical supplies, vaccines, and nutritional items, such as baby milk - but no food.
"Sources are telling me that the Syrian government did not allow all medical items - they certainly didn't allow surgical kits into Daraya," Bays said.
Fadi, a local activist, told the dpa news agency the convoy contained "no food supplies, only medical and school kits".
Another convoy, containing only food supplies and no medicine, entered into neighbouring Moadamiyah.
Bays said Wednesday was the deadline to decide whether there should be airdrops in Syria's besieged areas.
"On the day of the deadline for the start, perhaps, of an airdrop programme, the Syrian government, which hadn't been allowing convoys through, has allowed a little bit in," he said.
This was the deadline set by the international community. If aid wasn't going to get in by convoy they were going to start having air drops in Syria.
So UN officials are telling me every little bit helps, but they add this isn’t really enough.
Diplomats are saying that what they are seeing here is something we have seen so many times before; the tactics of the Syrian government, when confronted with a deadline, when confronted with an imminent Security Council meeting, they let in a little aid at the last minute.
Daraya, which lies in Western Ghouta outside the capital Damascus, has been under an increasingly tight government siege since 2012, with no access to essential services, such as running water and electricity.
No vaccinations have been carried out during that time.
Only about 8,000 people remain in Daraya, which had a population of about 80,000 before the war. But what little food can be grown locally is not enough, locals say.
On May 12, a five-truck aid convoy was turned back by the government in a dramatic 11th-hour rejection.
Wednesday's delivery came after Russia's foreign ministry said a local truce would be observed in Daraya for 48 hours to ensure the safe arrival of aid to the city's besieged population.
"On the initiative of Russia and in agreement with the leadership of Syria and the American side a 'regime of silence' has been introduced for 48 hours on June 1, 2016 from 00:01am in the settlement of Daraya to ensure the safe delivery of humanitarian aid to the population," Lieutenant-General Sergei Kuralenko said.
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Russia had last week called for a 72-hour "regime of silence" in Eastern Ghouta and Daraya amid deadlocked efforts to turn a cessation of hostilities into a lasting peace in the country.
The United States and Russia are co-partners in the so-called Vienna diplomatic process of the International Support Group for Syria, which met last month in the Austrian capital but made no notable progress.
At least 280,000 people have been killed and more than half of Syria's population have fled their homes since the conflict first erupted in 2011.
Source: Al Jazeera and agencies