Russian President Vladimir Putin said he hopes the US and its allies will do their best to avoid civilian casualties in an attack on Isis' Iraq stronghold of Mosul.

“We hope that our American partners, and in this case our French partners as well, will act selectively and do everything to minimise — and even better, to rule out — civilian casualties,” Mr Putin told a news conference after a summit of developing economies in India on Sunday.

“We of course are not going to fan hysteria over this matter, like our partners in the West do, because we understand that we need to fight terrorism, and that there is no other way apart from active fighting,” he added.

Mr Putin made his remarks as the UK and US said they were considering sanctions against Russia and Syria in response to their bombardment of Aleppo.

In pictures: Aleppo bombing Show all 14 1 /14 In pictures: Aleppo bombing In pictures: Aleppo bombing Bombing in Aleppo Smoke rises after airstrikes on the rebel-held al-Sakhour neighborhood of Aleppo, Syria April 29, 2016. Reuters In pictures: Aleppo bombing Bombing in Aleppo A Syrian family runs for cover amid the rubble of destroyed buildings following a reported air strike on the rebel-held neighbourhood of Al-Qatarji in the northern Syrian city of Aleppo, on April 29, 2016. AFP/Getty Images In pictures: Aleppo bombing Bombing in Aleppo A man reacts as he stands on blood stains at a site hit by airstrikes in the rebel held area of Aleppo's al-Fardous district, Syria, April 29, 2016. Reuters In pictures: Aleppo bombing Bombing in Aleppo The damage of the airstrikes in the rebel-held area of Aleppo on April 28 Reuters In pictures: Aleppo bombing Bombing in Aleppo The damaged the Medecins Sans Frontieres (MSF)-backed al-Quds hospital after it was hit by airstrikes, in a rebel-held area of Syria's Aleppo Reuters In pictures: Aleppo bombing Bombing in Aleppo Syrians evacuate an injured man amid the rubble of destroyed buildings following an air strike on a rebel-held of Aleppo on April 29, 2016. AFP/Getty Images In pictures: Aleppo bombing Bombing in Aleppo People inspect the damage at a site hit by airstrikes, in the rebel-held area of Aleppo's Bustan al-Qasr AP In pictures: Aleppo bombing Bombing in Aleppo A man leads a woman in tears and child out of the scene after airstrikes hit Aleppo AP In pictures: Aleppo bombing Bombing in Aleppo Civil defence members search for survivors after an airstrike at a field hospital in the rebel held area of al-Sukari district of Aleppo Reuters In pictures: Aleppo bombing Bombing in Aleppo A Syrian boy is comforted as he cries next to the body of a relative who died in a reported air strike in the rebel-held neighbourhood of al-Soukour in the northern city of Aleppo Getty Images In pictures: Aleppo bombing Bombing in Aleppo A Syrian family walks amid the rubble of destroyed buildings following a reported air strike in the Bustan al-Qasr rebel-held district of the northern Syrian city of Aleppo Getty Images In pictures: Aleppo bombing Bombing in Aleppo Syrian civil defence volunteers and rescuers remove a baby from under the rubble of a destroyed building following a reported air strike on the rebel-held neighbourhood of al-Kalasa in the northern Syrian city of Aleppo Getty Images In pictures: Aleppo bombing Bombing in Aleppo Syrians help a wounded youth following an air strike on the Fardous rebel held neighbourhood of the northern Syrian city of Aleppo Getty Images In pictures: Aleppo bombing Bombing in Aleppo Syrian civil defence volunteers evacuate people from a damaged building following a reported airstrike in the rebel-held neighbourhood of Tareeq al-Bab in the northern city of Aleppo

Foreign Secretary Boris Johnson warned Russia and Syrian president Bashar al-Assad that they would not be successful in their "barbaric siege" of the city.

Speaking in London following talks on Syria's civil war, US Secretary of State John Kerry said the bombardment constituted “crimes against humanity”.

Loading....

He said: “It could stop tomorrow morning, tonight if Russia and the Assad regime were to behave according to any norm or any standard of decency, but they’ve chosen not to.

“Instead we see what can only be described as crimes against humanity taking place on a daily basis, and hospitals are bombed and children are bombed or gassed.”

More than 275,000 civilians in the city are enduring daily bombing raids, alleged gas attacks, and the use of highly destructive barrel bombs from Russian and Syrian air strikes.

Boris Johnson calls for protests outside the Russian Embassy over Syria conflict

The battle to seize Mosul from Isis began on Monday morning, as convoys of troops began mobilising east of the city.

US and French forces had already began bombing Isis targets in the city ahead of the offensive.

Ahead of the battle, the Iraqi army dropped tens of thousands of leaflets over Mosul, urging residents to hide before the offensive beigns.

The leaflets carried several messages to the citizens attempting to reassure them that the advancing army "would not target civilians," but warned them to avoid the known locations of Isis militants.

The military operation is the most complex carried out in Iraq since US forces withdrew from the country in 2011.