NEW YORK – Britain, France and United States have requested an urgent UN Security Council meeting on Sunday on the escalating campaign in Syria’s second city of Aleppo.

According to several diplomats, the Security Council is expected to meet at 14:00 GMT).

Intense air strikes killed at least 45 civilians in Aleppo on Saturday alone, after Syrian government announced fresh campaign to retake the rebel-held city.

A week-long ceasefire agreed between the United States and Russia ended on Monday and efforts to revive the truce failed.

Earlier, in a statement, UN Secretary General Ban Ki-moon said he was appalled by the chilling upsurge in fighting in Aleppo and warned that the use of advanced weaponry in the battleground city could amount to war crimes.

Ban cited reports of air strikes involving use of incendiary weapons, bunker buster bombs and other powerful munitions in the offensive launched by the Syrian army two days ago to recapture the city.

He warned that the apparent systematic use of these types of indiscriminate weapons in densely populated areas may amount to war crimes.