GENEVA/UNITED NATIONS - The situation in Syria "looks calmer" as of Thursday afternoon, UN Secretary-General Ban Ki-moon said here Thursday, the first day of UN-mediated ceasefire in Syria.

"The world, however, is watching with skeptical eyes, since many promises previously made by the Government of Syria have not been kept," the UN chief said.

He urged the Syrian government to fully implement its commitment under the six point blue-print. He also called on the Syria opposition to stop violence in all its forms.

"This is time for the fundamental change of course. Too many lives have been lost, and it's time to stop the killing," said Ban, who is in Geneva to chair the UN Chief Executive Board Meeting, which gathers heads of the UN system, specialized agencies, funds and programs.

"We are working to send an observer team as promptly as possible," he said.

The UN chief said he had spoken with UN-Arab League joint envoy for Syria Kofi Annan.

Annan would dispatch Norwegian general Robert Mood and his team as early as Friday "as a way of preparing this observer mission," Ban said.

Annan said Thursday he is encouraged by reports that the cessation of hostilities in Syria "appears to be holding" and urged all Syrian to seize opportunities to implement the agreed six-point peace plan.

"I am encouraged by reports that the situation in Syria is relatively quiet and that the cessation of hostilities appears to be holding," Annan said in a statement released in Geneva as he briefed the UN Security Council on the latest development of Syria via video-link.

"All parties have obligations to implement fully the six-point plan. This includes both the military provisions of the plan and the commitment to move to a political process," he said.

Annan's six-point plan calls for a troop withdrawal from populated areas by April 10 and a ceasefire by April 12. The plan aims to pave the way for a political solution to the 13-month unrest.

"I urge all Syrians to seize the opportunity," Annan said in the statement.

Meanwhile, he also pointed out that the ceasefire is fragile, which makes it necessary to deploy a mission of observers to monitor implementation of the six-point plan.

Annan said Ban will be asking the Security Council for approval of the deployment of a UN Observer Mission as soon as possible.

"This will allow us to move quickly to launch a serious political dialogue that will address the concerns and aspirations of the Syrian people," Annan said.

The joint envoy also urged the Security Council to demand the withdrawal of troops and heavy weapons from towns in Syria.

On Wednesday, Annan received a letter from Syrian foreign minister on the Syrian government's decision "to cease all military fighting throughout Syrian territory" by 6 a.m. Damascus time (0300 GMT) on Thursday.

However, the Syrian government also said to reserve "the right to respond proportionately to any attacks carried out by armed terrorist groups against civilians, government forces or public and private property."