In a statement, Jaish al-Islam said the imprisoned fighters would be sent to a rebel-held area in northwest Syria.
A convoy was unable to finish unloading on Monday because of continued fighting, bringing in the remaining undelivered food parcels on Friday despite bombardment nearby.
Government troops and allied militia have recaptured half of the besieged region in a blistering assault launched on Feb 18.
Western powers, however, blame the Syrian government and Russian Federation for the crisis.
"Shelling in proximity of Douma (in) eastern Ghouta today is putting the. convoy at risk", said United Nations resident coordinator Ali al-Za'tari said.
The offensive has killed more than 975 civilians, including more than 200 children, and wounded several thousand people, according to the Observatory.
09 de marzo de 2018, 16:37Damascus, Mar 9 (Prensa Latina) A convoy with humanitarian assistance, including 13 truckloads of food, entered the eastern Ghouta region of eastern Syria, where terrorist groups are preventing local residents from moving to safer areas.
Fresh shelling of Eastern Ghouta endangered a vital aid delivery on Friday, almost three weeks into a blistering Syrian regime offensive that has seized more than half of the rebel enclave.
The Syrian regime's bombardment of rebel-held eastern Ghouta has now claimed the lives of more than 1,000 civilians, according to the Syrian Observatory for Human Rights.
The Syrian army was advancing near Mesraba and Mudeira, two small towns which represent the last link between the northern and southern halves of the enclave, which is located near to the Syrian capital, Damascus.
The cease-fire endorsed more than a week ago by the United Nations Security Council - but not yet implemented - does not cover H.T.S., a coalition of rebel forces led by the Nusra Front, a group that was formed as Al Qaeda's Syria affiliate and is listed internationally as a terrorist group.
The military gains have caused wide-scale internal displacement as civilians flee government advances toward areas in the territory still held by the rebels. The roads connecting the towns to each other were all covered by army fire, the Observatory said.
Almost 400,000 people are believed to be inside eastern Ghouta.
That has in effect cut the large towns of Harasta and Douma off from each other and the rest of the enclave, it added.
The Observatory and the opposition's Syrian Civil Defense, also known as the White Helmets, reported that airstrikes and shelling resumed late Friday afternoon on eastern Ghouta.
Residents will have to rely on unpaved roads to move in eastern Ghouta, but that is hard because of the intensity of shelling and airstrikes, activists said.