Syrian President Bashar al-Assad granted an amnesty on Sunday for crimes committed since the outbreak of a 10-month-old uprising against his rule, the state news agency SANA reported.
Opponents of Assad said the amnesty was meaningless because most detainees were held without charge in secret police or military facilities with no due process or legal documentation.
SANA said the amnesty for "crimes committed in the context of the events that occurred from March 15, 2011, until January 15, 2012" would run to the end of January for army deserters and people who possessed illegal arms or who violated laws on peaceful protest.
Syria's Addounia television said Arab League monitors discussed the amnesty with Damascus police on Sunday.
The amnesty was announced days before the monitors, who began work on Dec. 26, are due to report to the League on whether Syria is complying with an Arab League peace plan.
Under the plan, Syria's government agreed to free detainees, as well as to halt the bloodshed, withdraw the military from the streets and start a dialogue with the opposition.
Assad's critics derided the amnesty as a sham.
"The problem is not those who have reached trial or have been sentenced to terms in civic jails but those who are imprisoned and we don't know where they are or anything about them," said Kamal Labwani, who was freed last month after six years as a political prisoner and is now in Jordan.
The Avaaz advocacy group said on Dec. 22 that at least 69,000 people had been detained since the start of the uprising, of whom 32,000 had been released.
Assad has issued several amnesties since the start of protests, including one announced as recently as Nov. 4, but opposition groups say thousands of people remain behind bars and that many have been tortured or abused.
British Foreign Secretary William Hague questioned whether the amnesty offer was genuine.
"The Syrian government has had a habit of announcing amnesties and then making it impossible to verify whether they have really been implemented," he told Sky News television.
Mazen Adi, a veteran Syrian activist who spent two months in jail last year during the uprising, said Assad only wanted "to appear to adhere to the demands of the Arab League".
He said the decree excludes some charges under which anti-Assad activists have been jailed, such as "belonging to a secret society with the purpose of toppling the governing system".
Adi said more people were being detained every day and there was no guarantee that arrests of peaceful protesters would stop.
"You still have no right to demonstrate peacefully in Syria. Nothing prevents another wave of arrests of demonstrators who will be again held indefinitely," he said.
"Huge numbers of detainees are in secret police headquarters and complexes. The problem is not a judicial or legal issue because those detainees spend months before they are referred to the courts," Adi said.