Russia on Saturday vetoed a UN draft resolution demanding an end to the bombing of Aleppo but a rival measure it put forward on a ceasefire in Syria's war-battered city was rejected.
The failure of the two resolutions deepened divisions at the Security Council between Russia, Syria's ally, and the western powers backing opposition rebels in the war.
It was the fifth time that Moscow used its veto to block UN action to end the five-year war in Syria, which has claimed 300,000 lives.
Nine countries including Britain, France and the United States voted against the Russian measure while four countries backed the text that called for a ceasefire but did not mention a halt in the air strikes.
As the council meeting got underway, the Syrian regime pressed its assault on rebel-held areas of Aleppo, where 125,000 people are living under siege and facing almost-daily heavy bombing.
French Foreign Minister Jean-Marc Ayrault urged the council to take immediate action to save Aleppo from being destroyed by the Russia-backed Syrian bombing campaign.
"What is at stake today is first and foremost the fate of Aleppo and its people," Ayrault told the council.
"But it's more than that -- it's the hope of establishing at last an end to a conflict for which we are all, all of us, paying the catastrophic consequences."
In a message directed at Russia, Ayrault said any country that opposes the French measure will "give Bashar al-Assad the possibility of killing even more."
The measure presented by France won 11 votes in favor in the 15-member Security Council, but Russia and Venezuela voted against.
China, which had in the past backed Russia to block resolutions on Syria, abstained, as did Angola.
Shortly after the Russian veto, the Security Council rejected the rival draft presented by Moscow by a vote of nine against, four in favour and two abstentions.
Russia, China, Egypt and Venezuela voted in favour of the Russian measure while Angola and Uruguay abstained.
"A lonely veto and just four votes in favor of your text," British Ambassador Matthew Rycroft told the Russian ambassador after the second vote.
"A double humiliation", he called it.
Russian Ambassador Vitaly Churkin said he expected his draft text to be rejected, but stressed that he had warned France repeatedly that its measure was "doomed."
The Syrian and Russian bombing campaign has escalated since the Russian-backed Syrian army launched an offensive to retake the city on September 22.
German Foreign Minister Frank-Walter Steinmeier warned that the mounting tensions between Washington and Moscow over the conflict had created a situation "more dangerous" than the Cold War.
- Syrian army advancing -
Since the regime offensive began a few days after a US- and Russian-brokered ceasefire collapsed, at least 290 people -- mostly civilians -- have been killed in rebel-held areas, 57 them children, the Syrian Observatory for Human Rights reported.
And 50 civilians including nine children have been killed in rebel shelling on regime-held areas of the city, according to the Britain-based monitoring group, which relies on a network of sources on the ground.
It said government forces were making further advances on Saturday ahead of the Security Council session.
"The battle is unfolding in the center, particularly in the Bustan al-Basha district where the army is advancing, in Sheikh Said in the south, and on the northern outskirts where the regime has taken the Uwaija neighborhood," Observatory chief Rami Abdel Rahman told AFP.
The monitor reported heavy air strikes on the rebel-held Fardos and Sukari neighborhoods. An AFP correspondent said the raids mostly hit combat zones in the city.
The German foreign minister said that tensions between Washington and Moscow were now worse than during the Cold War.
"It's a fallacy to think that this is like the Cold War," Steinmeier said in an interview published by Bild newspaper.
"The current times are different and more dangerous."
US Secretary of State John Kerry made clear his anger at the Syrian army's Russian-backed onslaught in the battleground second city, saying that its bombing of civilians could amount to a war crime.
