UNITED NATIONS -- United Nations Secretary-General Ban Ki-moon on Friday welcomed the unanimous adoption by the UN Security Council of a resolution that endorses the cessation of hostilities in Syria, saying that its full implementation "is our best chance to reduce the brutal violence" in the Middle Eastern country.

On Friday afternoon, the Security Council adopted the resolution to endorse the joint statement announced on Monday by U.S. Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov, co-chairs of the International Syria Support Group (ISSG) Ceasefire Taskforce, on the terms of a nationwide cessation of hostilities in Syria

The Security Council demanded that the agreement take effect at midnight Damascus time on Friday.

"The full implementation of this resolution -- including unimpeded and sustainable humanitarian deliveries -- is our best chance to reduce the brutal violence in Syria," said a statement issued here by Ban's spokesman.

"What matters now are not the words of the resolution but whether it will make real changes on the ground and reduce the suffering of the Syrian people and create space and the credibility for the UN Special Envoy for Syria to relaunch political negotiation over transition in accordance with the Geneva Communique and resolution 2254," the statement said.

Resolution 2254, unanimously adopted by the 15-nation UN body in December, gave the UN an enhanced role in shepherding the opposing sides toward talks for a political transition, endorsing a timetable for a ceasefire, creating a new constitution and holding elections.

Briefing the Security Council by video conference just before the vote, the secretary-general's special envoy for Syria Staffan de Mistura, said that the cessation of hostilities was the result of lengthy and detailed discussions and intense negotiations at the highest level.

Speaking via videoconference from Geneva, he noted that it was a "major achievement."

Noting much work remains for the implementation of the agreement ahead, the UN envoy stressed that Saturday would be a critical day.

The international community must work fast to address any incidents that may arise, while all parties must demonstrate restraint, he said, adding that, provided the cessation of hostilities held and humanitarian access was kept open, he intended to reconvene formal Syria peace talks in Geneva on Monday.

In the new resolution, the Security Council also demanded that all parties involved in the cessation of hostilities fulfil their commitments, and urged all UN member countries to use their influence to help "create conditions for a durable and lasting ceasefire."

The resolution also reiterated its call to the parties to immediately allow humanitarian agencies "rapid, safe and unhindered access" throughout Syria by the most direct routes, and to immediately comply with their obligations under international law.

In the resolution, the Security Council welcomed the cessation of hostilities as a "step towards a lasting ceasefire," reaffirming the close linkage between a ceasefire and a parallel political process, and that both initiatives should move ahead "expeditiously" as expressed in resolution 2254.

More than 250,000 people were reportedly killed since the outbreak of the Syrian crisis and subsequent armed conflict in March 2011.