A Syrian student studying in Jordan, with his face painted in the colours of the Syrian opposition flag, shouts slogans against Syria's President Bashar Al-Assad during a demonstration in front of Syria's embassy in Amman.

New York - Fighting in Syria continues despite Syrian government assertions that it will comply with a UN-backed truce and has withdrawn troops and heavy weapons from cities and towns, the UN political affairs chief said on Monday.

More than 9 000 people have died in Syria during 13 months of fighting sparked by a popular uprising against President Bashar al-Assad. At least 20 people were killed in shelling on Monday, activists said.

“The cessation of armed violence remains incomplete,” Lynn Pascoe, UN undersecretary-general for political affairs, told the 15-nation Security Council during an open debate on the Middle East.

“Too many lives have been lost, human rights violations are still perpetrated with impunity. It is our hope that the deployment of observers will help to stop the killing and consolidate the calm,” Pascoe said.

The UN Security Council unanimously adopted a resolution on Saturday that authorised an initial deployment of up to 300 unarmed military observers to Syria for three months to monitor a shaky truce implemented earlier this month.

But the resolution conditions the deployment of observers on a UN assessment of compliance with the truce, reflecting US and European concerns that Damascus' failure to halt the violence, return troops to barracks and withdraw heavy weapons from towns makes the prospects for success slim.

“We are all sober in our expectations,” US Ambassador to the United Nations Susan Rice, who is president of the Security Council for April, told the council.

“The regime's long track record is one of dependable deceit and deception,” she said. “Thus this UN mission is unusually risky and dangerous. The Syrian regime should make no mistake, we will be watching its actions day and night.”

Syrian Foreign Minister Walid al-Moualem wrote to UN-Arab League peace envoy Kofi Annan, who brokered the truce, on Saturday to inform him that Damascus has now withdrawn heavy weapons and troops from Syrian cities, according to Syria's UN envoy, Bashar Ja'afari.

French UN Ambassador Gerard Araud told the council the situation on the ground was still of deep concern.

“The Syrian army has only misled us in terms of its withdrawal. Bombing and heavy weapons continue to be used,” he said. “No impediment to the actions of the observers, no threat to their security, should be tolerated by the council.”

Annan is due to brief the Security Council on Tuesday.

“Measures taken by the Syrian authorities to date, including on the release of arbitrarily detained persons and the respect of the right to demonstrate peacefully, are clearly insufficient,” Pascoe said.

UN Secretary General Ban Ki-moon will also brief the Security Council every 15 days about developments in Syria and submit to the Security Council proposals as needed for adjusting the mandate of the observer mission, to be called UNSMIS.

The UN Council also noted in Saturday's resolution that the cessation of violence by the government and opposition in Syria is “clearly incomplete” and warned that it could consider “further steps” in the event of non-compliance with its terms.

The United States, Britain and France both reiterated this warning during the Security Council debate.

“Failure of the regime to meet its commitments or any attempt to hinder work of the mission must be met by real and robust consequences,” British UN envoy Mark Lyall Grant said.

China and Syrian ally Russia, who have twice vetoed resolutions condemning Assad's government, said the international community needed to fully support Annan's peace efforts and action by the Security Council.

Moscow has been critical of other bids to end the violence by groups like the 14-nation “Friends of Syria”, saying it could undermine Annan's plan. Russian UN envoy Vitaly Churkin also described placing sanctions on Syria as counterproductive. - Reuters