Foreign Secretary Philip Hammond demanded Russia to comply with international law and the United Nations Security Council resolutions they signed up to and stop the "indiscriminate bombing of civilian areas" held by forces opposed to Syrian President Bashar al-Assad.
"The situations is Aleppo is extremely worrying," Hammond told the BBC's Andrew Marr Show. "The Russians are using carpet bombing tactics, indiscriminate bombing of civilian areas held by oppositionists." He added: "We demand that the Russians comply with their obligations under international law and they comply with their obligations under UN Security Council resolutions that they have signed up to."
Despite "ferocious" Russian air attacks over the last few weeks, Hammond claimed that forces loyal to Assad's regime did not have "the strength and the organisation to take control" of areas abandoned by opposition forces after the bombardment. "The Russians are only using air power," he said. "They can force the opposition to give ground but the regime has not shown itself able to effectively take control of that ground."
The result had been "attrition" between Assad's forces and around 150,000 moderate opposition forces on the ground, he said.
Calling Russian claims that a world war would erupt if Saudi Arabia, Qatar and other Arab countries entered the conflict "a gross exaggeration", Hammond said that the Sunni Arabs in the Gulf are nonetheless "deeply concerned" by Iranian forces engaging in the war.
"The fact that there are Iranian forces on the ground in Syria is a deeply destabilising factor," he said. "If the Russians are concerned about this, they should be prevailing on their Iranian allies to withdraw their forces."