France, Britain and their allies at the UN Security Council on Wednesday pushed Russia to end its bombing of Syria's Aleppo province and press the regime to allow humanitarian aid.

Russian Ambassador Vitaly Churkin shot back that Moscow would not be "apologetic" about its military campaign and suggested Western powers were using the pressing need for aid deliveries in Syria for propaganda ends.

The Security Council met at the request of New Zealand and Spain to discuss the crisis in Aleppo where tens of thousands of people are fleeing a Syrian government offensive, backed by Russian air power.

The appeals to Russia came on the eve of a crucial meeting in Munich of the 17-nation International Syria Support Group that is to chart a way forward for peace talks set to resume in Geneva on February 25.

Up to 35,000 people have fled the Russian-backed assault in northern Syria in recent days, according to the United Nations, with tens of thousands massing on the border with Turkey.

Russian Foreign Minister Sergei Lavrov is to present ceasefire proposals at the Munich talks, but no details of the plan were released at the council meeting.

"Let me be clear about it: It's not a favor that we are asking to the Syrian regime and its allies, it's their obligation," French Ambassador Francois Delattre told reporters.

"The regime and its allies cannot pretend they are extending a hand to the opposition while, with their other hand, they are trying to destroy them," he said.

Humanitarian pause

New Zealand and Spain proposed a humanitarian pause to shore up prospects for the peace talks after the opposition said it would not attend without an end to starvation sieges and air strikes.

"We do call on them to show decency and cooperate with the UN," said New Zealand Ambassador Gerard van Bohemen.

Russia's envoy said Moscow was ready to look at proposals for a humanitarian pause but that discussion would be needed to avoid the same outcome as in Yemen, where ceasefires never materialized.

"We are not about to be apologetic about what we are doing," Churkin told reporters after the meeting.

"We are there legally, at the invitation of the Syrian government."

"This propagandistic use of the Syrian humanitarian file is not going to deter Russia from doing the humanitarian work we are doing with the Syrian government," he added.

President Bashar Al-Assad's forces backed by Russian warplanes have captured a string of villages around opposition-held Aleppo over the past week and managed to cut a major rebel supply route to the city.

Churkin commented that the "changes in balance on the ground... should be taken as logical development in any armed conflict."

Syria's nearly five-year-old war has killed 260,000 people and displaced half the population.