People wave Turkish and Free Syrian Army flags during a gathering before the departure of a Syria-bound aid convoy, carrying humanitarian supplies, in Istanbul, Turkey, December 14, 2016. (Xinhua/REUTERS)

UNITED NATIONS, Dec. 21 (Xinhua) -- The UN Security Council Wednesday adopted a resolution to extend the cross-border aid deliveries to Syria for one year.

The 15-nation council expressed outrage at the "unacceptable and escalating level of violence" and the killing of well over a quarter of a million people as a result of the Syrian conflict.

Therefore, it requested the Syrian authorities to expeditiously respond to all requests for cross-line deliveries submitted by the United Nations and their implementing partners and to give such requests "positive consideration."

The resolution extended until Jan. 10, 2018 the authorization which allows the UN and its implementing partners to deliver humanitarian assistance across borders and conflict lines.

On Monday, the Security Council decided to send UN observers to monitor evacuations in Syria's war-torn Aleppo where tens of thousands of civilians remain trapped.

The conflict in Syria broke out in March 2011. An estimated 13.5 million people are in urgent need of assistance.