The league official said an advance team of monitors was back in Cairo Sunday after spending 10 days in Syria, but the main group of observers dispatched last week was still in Syria, CNN reported Monday.
Arab League observers traveled to Syria in December after the United Nations estimated at least 5,000 people had been killed since March in an uprising against President Bashar Assad's government. Assad said his forces are combating terrorists and thugs.
The advance team that returned to Cairo will prepare a report to be released soon, the league official said.
Egypt's state-run Middle East News Agency reported the leader of an Arab League advisory board called for the withdrawal of observers from Syria, saying the mission allowed Syrian officials to maintain a brutal crackdown on protesters.
"What is happening allows the Syrian regime a cover for the exercise of its inhumane practices under the Arab League's watch," Ali Salem al-Deqbasi said in a statement.
An opposition group said at least 10 people died Sunday while the fact-finding mission monitored whether Assad was fulfilling his commitment to end the crackdown on protesters.
Last month, Assad agreed to a peace initiative with the Arab League that called for security forces to withdraw from cities, the release of detainees and an end to violence.
A group called the Local Coordination Committees of Syria said Sunday it has documented the deaths of at least 315 people since Arab League monitors arrived.
The BBC reported Arab League observers provided apparently conflicting accounts of an incident that reportedly involved snipers in the restive city of Daraa.
Video posted on the Internet appears to show one official saying he saw government snipers posted on rooftops and urged that they withdraw. The head of the mission, Sudanese Gen. Mustafa al-Dabi, later denied that the monitor actually saw any snipers.
"This man said that if he saw -- by his own eyes -- those snipers he will report immediately," Dabi told the BBC. "But he didn't see [snipers]."
Dabi has come under fire by protesters who want him removed from his leadership role, saying he is biased in favor of the Syrian government.
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