There have been problems rehabilitating ex-Tamil Tiger fighters into society, the Sri Lankan authorities say.
They say some have been taken back in for police questioning after being freed, but that those numbers are not high and the releases continue.
The Brussels-based International Crisis Group says it has heard of freed rebels being subject to "frequent, arbitrary questioning" by security forces.
The 26-year civil war ended when the insurgents were defeated in May 2009.
The army says more than 11,000 Tamil Tigers handed themselves in and were taken into custody in the war's final stages.
The army has been putting the detained ex-members of the Liberation Tigers of Tamil Eelam (LTTE) through a "rehabilitation" process.
The officer in charge of the programme, Brigadier Sudantha Ranasinghe, told the BBC that half of the former rebels - about 5,600 - have been released in batches since early last year, returning to their home areas.
'Stealing and brewing'
Yet there have been rumours that the process has not always gone smoothly.
Brig Ranasinghe says some former rebels have been taken in for questioning because of complaints by villagers that the ex-combatants were stealing or brewing illicit liquor.
The Geneva-based International Organization for Migration, the only major international agency working to help reintegrate the ex-fighters, said last month the former Tigers were being treated quite well.
Brig Ranasinghe said the ongoing rehabilitation programme included "de-radicalisation" and skills training.
The government says about 4,600 rebels who surrendered are still undergoing rehabilitation.
Brig Ranasinghe was unable to give a timetable for their eventual release, but he said they would continue to be freed in batches.