Authorities in Syria have released 755 prisoners who were detained in the government crackdown on dissent over the past nine months, the country's state-run news agency said.
Sana said the release excludes prisoners with "blood on their hands".
The release of prisoners is one of the terms of the Arab League peace plan to stop the bloodshed in Syria and comes a day after Arab monitors were allowed to deploy in the country to ensure authorities are complying with the plan.
US-based Human Rights Watch (HRW) has accused Syrian authorities of hiding hundreds of detainees from the observers now in the country.
The New York-based group said the detainees have been transferred to off-limits military sites and urged the observers to insist on full access to all sites used for detention.
HRW's report, issued late on Tuesday, echoes charges made by Syrian opposition members that thousands of detainees were being transferred to military sites ahead of the observers' visit.
Syrian officials have said the Arab League monitors will have unrestricted access to trouble spots but will not be allowed to visit sensitive military sites.
"Syria has shown it will stop at nothing to undermine independent monitoring of its crackdown," said Sarah Leah Whitson, Middle East director at Human Rights Watch. She said it was essential for the Arab League "to draw clear lines" regarding access to detainees, and be willing to speak out when those lines are crossed.
Last month, Syrian authorities released 2,645 prisoners in three batches but activists and critics say thousands more who were picked up in the past months remain in jail.
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