Half of the members of the United Nations observer mission in Syria have left the country, two mission members told AFP on Wednesday.
"One hundred and fifty observers left Syria on Tuesday evening and Wednesday and they will not come back," one observer told AFP, speaking on condition of anonymity.
"They left after a decision was taken to reduce the mission by half," a second observer said, without specifying who had taken the decision.
The UN Supervision Mission in Syria, as the force is officially known, consists of 300 unarmed military observers accompanied by around 100 civilian support staff.
It was deployed in April to oversee a ceasefire that went largely unrespected and in mid-June stopped carrying out patrols as fighting intensified.
On July 20, the UN Security Council voted to extend the mission's mandate for a "final" 30 days, with Western nations warning that the continued violence meant it was unlikely the observers would be able to remain in country.
US ambassador Susan Rice said the resolution would allow the observers "to withdraw safely" from Syria, while British Foreign Secretary William Hague said the resolution gave President Bashar al-Assad's government "the final chance" to keep its commitment to end violence.
But Russian ambassador Vitaly Churkin insisted that the phrase "final period of 30 days" in the text was not the death knell for UNSMIS and that its work should continue.
"This is not a resolution about withdrawal, it is a resolution about continuation of the activity of the mission," he said.