New Delhi: In a recent development US Secretary of State John Kerry has issued a stern warning to Russia and Syria asking them to end all attacks on Aleppo.

The State Department said John Kerry issued the ultimatum in a Wednesday telephone call to Russian Foreign Minister Sergey Lavrov. 

US Secretary of State Spokesperson John Kirby said Kerry expressed grave concern over Russian and Syrian government attacks on hospitals, water supplies and other civilian infrastructure in Aleppo.

John Kirby also said John Kerry told Lavrov that the US holds Russia responsible for the use of incendiary and bunker-buster bombs in an urban area.