The wounded and dazed Aleppo boy whose image has shocked the world became the focal point of a UN Security Council discussion on Syria on Monday as a top UN official and members of the council pleaded for humanitarian pauses in the Syrian city.

During the council's monthly discussion on the humanitarian situation in Syria, almost every member of the council referenced images of 5-year-old Omran Daqneesh sitting in an ambulance covered with debris and blood as a symbol of destruction in the northern city of Aleppo.

Omran and his family were pulled from under the rubble last week after a military strike on the rebel-held Qaterji district. His 10-year-old brother, Ali, died from his wounds on Saturday.

"Just pause for a moment and imagine this was your child, a child that has known nothing but horrific war," said UN humanitarian affairs chief Stephen O'Brien.

"That is the reality of what is at stake this morning here in this chamber - not the politicking and posturing, the power games and defensiveness - all we need is for the guns to fall silent."

O'Brien warned that Aleppo might turn into "a humanitarian catastrophe unparalleled ... in the Syrian conflict."

He welcomed Russia's support for a proposal to hold regular 48-hour humanitarian pauses in the city, however, he noted that all parties need to agree to such a measure to allow aid workers to begin delivering assistance.

An estimated 275,000 people are living under siege in the city's rebel-held eastern part, while up to 1.5mn are also in need of humanitarian aid in the city's government-held western parts.

"As the UN's humanitarian chief, this callous carnage that is Syria has long since moved from the cynical to the sinful," O'Brien said, pleading with council members to unite.