NEW YORK

Billions of dollars raised for Syria at an international donor conference in London is a sign the world has recognized the necessity of sharing the refugee burden on Syria's neighbors, a UN spokesman said Thursday.

Farhan Haq told reporters in New York that Turkey, Lebanon and Jordan had been "extremely generous in allowing people to enter across the border and escape the fighting inside Syria", but the burden on them must be eased.

"We hope that ... the progress we've made today in London indicates a sign that the rest of the world has seized the serious nature of the challenge they faced and appreciates the need to share the burden and responsibility of taking care of so many people fairly," Haq said.

The single-day Syrian Donors Conference -- jointly hosted by Britain, Germany, Norway, Kuwait and the United Nations -- has raised more than $10 billion in pledges to aid Syrians displaced by war.

The conflict, which will enter its sixth year next month, has killed more than 250,000 victims and made the country the world's single largest source of refugees and displaced persons, according to UN figures. Nearly 5 million live as refugees in neighboring countries.

Turkish Prime Minister Ahmet Davutoglu warned Thursday that an estimated 70,000 Syrians from camps in northern Aleppo are now fleeing toward Turkey as a result of recent Russian airstrikes.

As the largest refugee-hosting country in the world, Turkey has spent nearly $8 billion caring for more than 2.5 million Syrian refugees on its soil.