'Limbs' of Aleppo children at door of Russian embassy

Standing among 800 white mannequin limbs strewn across the pavement were 25 activists - two of them locked to the gate - from The Syria Campaign and Syria Solidarity UK, protesting over Russia's carpet-bombing of the contested city.

"We're here because innocent children are being killed in their beds, while doctors are being bombed just for trying to save the lives of others," John Dunford from The Syria Campaign said.

"The Russian government and the Assad regime are committing these war crimes in Aleppo and things could be about to get even worse.

"We will not stand by and let this happen. This is a test of our shared humanity, a line we cannot cross. It shouldn't be up to activists like me to say this - the UK government should be doing far more to protect the innocent and stand up against this barbarity."

The campaigners are calling on the British Foreign Secretary Boris Johnson to increase the pressure on Russia, including by announcing new sanctions against Russian financial interests in the UK.

Russia is set to launch a major shock and awe assault on the embattled city as soon as this week, if reports are true, after rebels started a last ditch offensive to take west Aleppo from government control.

Warships and submarines have been sent to the region over the past few days, while leaflets dropped on residents have warned of "annihilation" if they fail to surrender.

Explaining the use of mannequin limbs, protester Anna Nolan said: "One story that I will never forget came from Rady, a young volunteer rescue worker from Idlib. After a Russian airstrike he rushed to the scene where him and his teammates found a man whose wife, daughter and newborn baby had been killed in an airstrike.

"After burying his wife and daughter, the man returned to the scene begging the rescue workers to dig to retrieve some part of his baby. He wanted something to hold onto. Something to bury.

"Such is the utter brutality of Russia's actions that ordinary Syrians, just like you or I, are left searching for the limbs of their loved ones."

Amr Salahi from Syria Solidarity UK, added: "The Russian government and Assad are shredding international agreements and laws that exist for the protection of all of us. To save Syria is to save ourselves."