Arab League monitors have gathered accounts about the Syrian government's crackdown on dissent in the central city of Homs, as fresh violence flared just miles away.
Activists said troops opened fire on thousands of unarmed protesters, killing at least six.
Though President Bashar Assad's regime has made concessions to the observers, including the release of nearly 800 prisoners, the military was pressing ahead with a campaign to put down mostly peaceful protests.
In the two days since the Arab monitors arrived, activists said troops have killed at least 39 people, including the six shot in the central city of Hama. The continued bloodshed - and comments by an Arab League official praising Syria's cooperation - have fuelled concerns by the Syrian opposition that the Arab mission is a farce and a distraction from the ongoing killings.
The opposition suspects Assad is only trying to buy time and forestall more international sanctions and condemnation. "This mission has absolutely no mandate, no authority, no teeth," said Ausama Monajed, a member of the Syrian National Council, the main opposition group. "The regime does not feel obliged to even bring down the number of casualties a day."
The 60 monitors - the first Syria has allowed in during the nine-month uprising - are supposed to be ensuring the regime is complying with terms of a plan to end a crackdown the UN says has killed more than 5,000 people since March.
The plan, which Syria agreed to on December 19, demands that the regime remove its security forces and heavy weapons from cities, start talks with the opposition and allow human rights workers and journalists into the country. It also calls for the release of all political prisoners.
On Wednesday the government released 755 prisoners following a report by Human Rights Watch accusing authorities of hiding hundreds of detainees from the monitors. It was the second concession in two days.
The army on Monday pulled some of its troops back from the central city of Homs after bombarding it for days and killing scores of people. Monitors who were allowed into the city were met by tens of thousands of protesters who called for Assad's execution.
Despite the ongoing crackdown, an Arab League official said cooperation by Syrian authorities with the monitors was "reassuring". "The Syrian side is facilitating everything," Adnan Issa al-Khudeir told reporters in Cairo.