Two former members of Syria's secret police have appeared in a German court accused of crimes against humanity for their role in a government-run detention centre where thousands of protesters were tortured.

Key points: It is the first time an international power has taken representatives of the Syrian Government to trial over war crimes

It is the first time an international power has taken representatives of the Syrian Government to trial over war crimes Several Syrian refugees will testify that the accused were complicit in their torture at a detention centre near Damascus

Several Syrian refugees will testify that the accused were complicit in their torture at a detention centre near Damascus The men themselves sought asylum in Germany prior to their arrest in early 2019

The trial is the first time that representatives of the Syrian Government have faced trial abroad for war crimes allegedly committed during the nation's years-long conflict.

The two men, who were arrested in Germany early last year, face testimony from several Syrian refugees who allege they were tortured at the detention centre known as Al Khatib, near Damascus.

Prosecutors allege one man was in charge of the site and thereby responsible for crimes against humanity, rape and the murder of at least 58 people.

The indictment by German prosecutors accuses him of complicity in more than 4,000 cases of torture. If convicted, he could face life imprisonment.

Several refugees will testify against the men, who are charged with crimes against humanity. ( Thomas Frey/dpa via AP )

The other man is accused of being part of a police squad that detained protesters and brought them back to Al Khatib where they were then mistreated — he faces up to 15 years in prison if convicted.

At least nine torture victims are represented as co-plaintiffs in the case, they and several others are expected to be called as witnesses.

"This trial is not only important for us personally" one witness said. "It is also important for the victims who are alive, who have also been in prison and also for the victims who are no longer alive."

"[This is] the first time in my life that I experienced a fair trial," said another co-plaintiff.

"We want to reveal the truth about the system of torture in Syria."

The trial has been described as a pivotal moment in the effort to bring Syrian officials accused of crimes to justice.

A United Nations expert panel published a report two years ago detailing the extent to which prisoner abuse is widespread in Syria, particularly in government detention centres.

"The criminal trial starting today for crimes against humanity by the Syrian regime is historic," said Germany's justice minister, Christine Lambrecht.

"For the first time thousands of instances of torture and abuse are being prosecuted before an independent court in Germany."

"This sends a clear message: War criminals must not feel safe anywhere."

The defendants' lawyers declined to comment to reporters ahead of the trial, which is scheduled to last several months.

The men, who themselves left Syria to seek asylum in Germany before their arrest in February 2019, remain in prison.

AP