Kremlin spokesperson Dmitry Peskov denounces US and UK's criticism of the renewed bombardment in Aleppo.
Defying international pressure, the Russian-backed regime in Syria intensified its air offensive against opposition-held parts of Aleppo on Monday, as the country's biggest city faced worsening food and medical shortages.
A fresh wave of severe air strikes battered Aleppo's opposition-controlled east, said an AFP correspondent in the city that has been facing its worst violence in years.
The UK-based Syrian Observatory for Human Rights (SOHR) monitor said at least 12 people, including three children, were killed in Monday's raids on several opposition-held districts.
It was the fourth day of intense bombardment since a defiant Syrian regime launched a new assault to retake all of Aleppo following last week's collapse of a short-lived ceasefire brokered by Moscow and Washington.
Since the truce fell apart, a total of 248 people have been killed in Aleppo city and the wider province by Russian and Syrian regime bombardment, the SOHR said.
A source in the Syrian regime said their forces had no intention of letting up on opposition-held areas.
"The air force will bomb any terrorist movements, this is an irreversible decision," the source said, adding that the regime's goal was to "recapture all regions of Syria" outside its control.
Moscow and Damascus say they are bombing only militants, although video from Aleppo has repeatedly shown small children being dug out of the rubble of collapsed buildings.
A medical source in opposition-held Aleppo said hospitals were struggling to deal with a huge number of casualties.
"Hospitals that are still in service are under a lot of pressure due to the significant number of wounded in recent days, and the major shortage of blood," the source said.
"Because of this, serious injuries are requiring immediate amputations."
Some 250,000 civilians remain trapped in the besieged, opposition-held sector of Aleppo.
Water and food shortage
Several charity kitchens in Aleppo's opposition-held east were closed in fear of strikes, while water remained cut after pumping stations were damaged at the weekend.
"We endured through years of bombardments and did not leave Aleppo. But now there is no bread, no drinking water, nothing in the markets. The situation is getting worse every day," said Hassan Yassin, a 40-year-old father of four.
On Monday, dozens of families quit the last opposition-held district of central Homs city as part of a deal struck with the regime last year.
Russia dubs criticism "unacceptable"
Kremlin spokesperson Dmitry Peskov denounced "the overall unacceptable tone and rhetoric of the representatives of the United Kingdom and the United States, which can damage and harm our relations".
During Sunday's emergency session of the United Nations Security Council (UNSC), the US, UK and France slammed the renewed bombardment of Aleppo.
US Ambassador to the United Nations Samantha Power had accused Russia of "Barbarism", while the French and British envoys called the Syrian regime's actions "war crimes".
Kerry defends talks
US Secretary of State John Kerry defended his efforts to negotiate with Moscow over the war in Syria on Monday.
Kerry said his failed ceasefire was not the cause of the fighting, and the only way to stop the war was to talk.
"The cause of what is happening is Assad and Russia wanting to pursue a military victory," Kerry told reporters during a trip to Colombia.
"Today there is no ceasefire and we're not talking to them right now. And what's happening? The place is being utterly destroyed. That's not delusional. That's a fact," Kerry said.
Syria's al Moallem says ceasefire 'not dead'
Syrian regime's Foreign Minister Walid al Moallem has said that US-Russia-brokered ceasefire agreement is still viable.
Al Moallem accused the US, Britain, and France of supporting "terrorists" inside Syria.
He, however, added that the continuing interaction between the US Secretary of State and his Russian counterpart Sergey Lavrov indicates that a truce deal reached two weeks ago is "not dead."
UN aid reaches four besieged towns
The United Nations World Food Programme (WFP) has said that life-saving food assistance has been delivered to four besieged towns of Madaya and Zabadani in Rural Damascus and Foaa and Kefraya in Rural Idlib.
The aid reached the besieged towns for the first time since April as part of a joint interagency convoy with UN agencies and the Syrian Arab Red Crescent (SARC), WFP said in a statement on Monday.
"This convoy has brought extraordinary relief for 60,000 people who are in dire need of food and medical supplies, and have been cut off from humanitarian access for five months," said WFP Syria Country Director Jakob Kern.
WFP sent 45 trucks carrying food rations and wheat flour to the four towns as part of a joint UN-SARC convoy.