Some 100 men from the Syrian city of Homs, who turned themselves in after escaping an army siege, have been sent to perform their military service, the governor said Monday.
Activists expressed concern over the fate of the men, with one warning that "there is a real chance they might get assassinated".
Homs governor Talal al-Barazi told AFP that the 118 men, who had been held at the city's Al-Andalus school, had been "freed" under a government amnesty announced last week.
But he added that all the men would be sent to the army to either begin or complete their military service.
"One hundred and eighteen men who were being held in the Al-Andalus school were released last Thursday as part of the amnesty decree" issued by President Bashar al-Assad, he said.
"Around half of them were defectors from the army, and the other half were civilians who had not yet performed their military service," Barazi said.
"Those who defected from the army (and joined the armed rebellion) will return to the military," he said.
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"Those among them who were civilians and had failed to perform their military service are now being dealt with by the concerned military authorities and will also perform their military service."
The men were among hundreds of people who had turned themselves in before the rebels' withdrawal from the Old City of Homs in May.
Most of the others were later released, although some 60 of them have since disappeared, including prominent activist Khaled al-Tellawy, according to fellow activists from Homs.
One activist who recently left Syria said the families of the Al-Andalus school detainees had become increasingly concerned about their whereabouts.
"Some of them have been in touch to say they are alive, and that they have been sent to military bases. But most of them have disappeared, their families know nothing about them.
"We are very worried that they will be sent to especially violent battlefronts, and that the officers in charge will themselves eliminate them, and then claim they were killed in fighting," the activist, who identified himself only as Thaer, told AFP.
Assad last week issued a wide-reaching amnesty decree, but activists have been able to confirm the release of only some 1,200 prisoners.