BEIRUT – As Syria's government consolidates control after years of civil war, President Bashar al-Assad's army is doubling down on executions of political prisoners, with military judges accelerating the pace they issue death sentences, according to survivors of the country's most notorious prison.

In interviews, dozens of Syrians recently released from the Sednaya military prison in Damascus described a government campaign to clear the decks of political detainees. The former inmates said prisoners are being transferred from jails across Syria to join death-row detainees in Sednaya's basement and then be executed in pre-dawn hangings.

Yet despite these transfers, the population of Sednaya's once-packed cells – which at their peak held an estimated 10,000 to 20,000 inmates – has dwindled largely because of the unyielding executions, and at least one section of the prison is now almost entirely empty, the former detainees said.

Some of the former prisoners had themselves been sentenced to hang, escaping that fate only after relatives paid tens of thousands of dollars to secure their freedom. Others described overhearing conversations between guards relating to the transfer of prisoners to their death. The men all spoke on the condition that their full names not be disclosed out of fear for their families' safety.

According to two former detainees who have passed through the Damascus field court, located inside the capital's military police headquarters, the rate of death sentences has accelerated over the past year as the attitudes of court officials hardened. These two men had each appeared twice before a military field court judge, once earlier in the war and once this year, and were able to compare the way this secretive court operates.

“There was no room for leniency on my second visit,” one man said. “Almost everyone in that room was sentenced to death. They were reading the sentences aloud.”

Even before they reach the gallows, many prisoners die of malnutrition, medical neglect or physical abuse, often after a psychological breakdown, the former detainees said.

One former prisoner said guards had forced a metal pipe down the throat of a cellmate from the Damascus suburb of Darayya. “They pinned him to the wall with it and then left him to die. His body lay among us all night,” said Abu Hussein, 30, a mechanic from the western province of Homs. Another described how prisoners in his own cell had been forced to kick to death a man from the southern city of Daraa.

Satellite imagery of the Sednaya prison grounds taken in March shows an accumulation of dozens of dark objects that experts said were consistent with human bodies. The imagery was obtained by the Washington Post, which asked forensic experts to review it.

“Present in the imagery from March 1st and March 4th of the prison, there are dark elongated objects, similar to each other, measuring approximately five to six feet in length,” said Isaac Baker, imagery analysis manager at the Harvard Humanitarian Initiative's Signal Program on Human Security and Technology. “While analysis and available data does not prove, it does corroborate, and is consistent with, eyewitness accounts of mass executions at this facility.”

Two former detainees held in cells nearest to the guardroom in their prison wing describe overhearing conversations between their jailers regarding executions in early March. “They were talking about a set of prisoners' bodies that had been moved to the yard,” one man said.

Other satellite imagery of military land near Damascus, previously identified by Amnesty International as a location of mass graves, appears to show an increase in the number of burial pits and headstones in at least one cemetery there since the start of the year. Defectors who worked in the military prison system said this area, located south of the capital, is the likely location for the mass burial of Sednaya prisoners.

In the cemetery on the road running south from Damascus, dozens of new burial pits and headstones have appeared since the winter.

After seven years of war, more than 100,000 Syrian detainees remain unaccounted for. According to the United Nations and human rights groups, thousands, if not tens of thousands, are probably dead.

Although all sides in the conflict have arrested, disappeared and killed prisoners, the Syrian Network for Human Rights monitoring group estimates that as many as 90 percent have been held across a network of government jails, where torture, starvation and other forms of lethal neglect are used systematically and to kill. At one point, Sednaya alone held as many as 20,000 inmates, according to Amnesty International.