A contingent of six United Nations observers arrived Sunday night in Damascus to pave the way for as many as 30 observers this week whose mission is to verify if both sides in Syria's civil conflict are abiding by a ceasefire that went into effect Thursday.

Now more than four-days old, the ceasefire has seen the level of violence throughout the country drop dramatically, but it still is plagued by sporadic outbursts mostly from government forces and mostly in the central Syrian city of Homs.

Five civilians were reportedly killed there Sunday in heavy shelling by Syrian forces.

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The ceasefire, negotiated by former UN secretary-general Kofi Annan, is key to a six-point plan intended to end the violence in the country that is believed to have killed more than 9,000 people in the past 13 months, and to launch a political process that will involve both the opposition and the regime of President Bashar al-Assad.

A disagreement at the United Nations Security Council that put the observer mission in jeopardy was overcome Saturday when the United States, Britain and France acceded to Russia's demands on the terms of deployment.

Vitaly Churkin, Russia's United Nations ambassador, said Moscow had objected to the one-sided nature of the U.S.-drafted resolution that blamed only the Syrian government for the conflict and threatened punishment for its crimes.

Russia also objected to the fact that the resolution included the deployment of a full contingent of some 250 to 300 observers and that Syria was required to give the force complete freedom of action inside the country .

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Moscow wanted the resolution to pin responsibility for the conflict on both the regime and the armed elements of the opposition, and it wanted the resolution to apply only to the advance team of some 30 UN observers. The balance of the observers and the terms of their deployment should be subject to Syrian agreement, Mr. Churkin says.

And Russia got exactly what it wanted.

The resolution adopted unanimously by the 15-member Security Council, applies only to the advance group of observers, blames both sides for the country's violence and pledges that the terms of any further observer forces' deployment would be agreed on only after consultations between UN Secretary-General Ban Ki-moon and the Syrian government.

The concessions show just how much the United States and its allies have come to accept that Russia is crucial to finding a political solution to the bloody mess in Syria.

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The Security Council resolution calls on both sides to "cease all armed violence in all its forms" and condemns "the widespread violations of human rights by the Syrian authorities, as well as any human-rights abuses by armed groups."

This is more balanced, said Mr. Churkin, who explained that Moscow was acting "out of respect for the sovereignty of Syria."

Bouthaina Shaaban, a spokeswoman for President al-Assad, said Syria reserved the right to refuse monitors depending on their nationality and to be involved, in other ways, in approving the observers' mission.

"The duration of the work of observers and priorities of their movement will be in co-ordination with the Syrian government because Syria cannot be responsible for the security of these observers unless it co-ordinates and participates in all steps on the ground," she told reporters in Damascus.

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The UN's Mr. Ban voiced concern Sunday over the continued shelling of Homs.

"I am very much concerned about what has happened since yesterday and today," Mr. Ban said Sunday after talks with Belgian Prime Minister Elio Di Rupo in Brussels.

"While we welcome this cessation of violence at this time, I warn that the whole world is watching with skeptical eyes whether this will be able to be sustainable," Mr. Ban said, adding that the truce-monitoring mission will be up and running from Monday.