Berlin: An Iraqi man accused of being an Islamic State terrorist has gone on trial in a high court in Frankfurt, Germany, accused of genocide, human trafficking, and the torture and murder of a 5-year-old Yazidi girl he had held as a slave in Fallujah, Iraq.

Opening statements in the trial of the defendant identified by his first name and last initial in accordance with German privacy rules, Taha Al-J., came a year after his German-born wife went on trial over the death of the same girl.

Iraqi Yazidi women mourn during the exhumation of a mass grave in Iraq's north-western region of Sinjar. AP

His trial is believed to be the first in the world that carries the charge of genocide in relation to the Yazidis.

"This trial is remarkable in many ways," Alexandra Lily Kather, an international law expert, said in a telephone interview. "This is the first case going on trial in the world including genocide among the charges with respect to crimes committed against the Yazidi." Kather co-authored a report on the trial's significance for Just Security, a legal blog.

Taha Al-J., who is 27, is also charged with murder, crimes against humanity, war crimes and trafficking for the exploitation of their manpower and murder, according to the counts read aloud by the president of the five-judge panel in Frankfurt on Friday. The defendant, dressed in a patterned button-down shirt, declined to make an opening statement or to enter a plea.

His trial centres on a mother and her child, members of the Yazidi religious minority who have been persecuted by the Islamic State, known as ISIS. The defendant and his wife bought, enslaved and tortured the five-year-old and her mother, prosecutors said. The girl died in 2015 after being left chained to the bars of window in heat reaching 50 degrees.

"Taha Al-J. intended, according to the charges, to exterminate the religious minority of the Yazidi by his acquisition of the two Yazidi females and to have personal benefits from their services in his household," Charlotte Rau, a court spokeswoman, said in a statement on Friday.

The defendant was captured in Greece and extradited to Germany a month after his wife's trial started.

The trials are part of a series in Western courtrooms dealing with the crimes committed by extremists from the Islamic State during their active years in Iraq and Syria as they tried to create a caliphate. Taha Al-J.'s trial is the second in Germany in as many days to rely on the legal concept of "universal jurisdiction," which tries foreign-born defendants for crimes committed abroad.

On Thursday, the trial of two Syrian men accused of torturing and killing people for their country's secret police got under way in Koblenz, roughly 120 kilometre north-west of Frankfurt. Like the trial of the German-born wife of Taha Al-J., other hearings in Germany have also focused on German citizens who had joined Islamic State.

The head of a United Nations commission in 2016 said of targeted attacks on the Yazidi minority in 2014: "Genocide has occurred. ISIS has subjected every Yazidi woman, child or man that it has captured to the most horrific of atrocities."

The mother of the child, who was unidentified, will be a witness and co-plaintiff in the trial. Her legal team includes human rights lawyer Amal Clooney.

Kather and other legal advocates — citing the fact that Islamic State fighters had separated captured Yazidi men and boys from women and girls, killing or recruiting the former and enslaving or raping the latter — have criticised this case for not emphasising the gender-specific nature of the genocide.

"We hope for gender-specific harm to be reflected or included in the charges of cases going to trial in the future," she said.

According to the indictment in Frankfurt, the defendant bought the mother and daughter and held them in his household in Fallujah in the summer of 2015, where they were forced to keep house under strict Islamic rules. The prosecutors say the two were not given enough food or water and were regularly beaten.

The weakened child died after she was chained in direct sunlight in late summer of that year. During that time, Taha Al-J. ran the bureau of "Shariah exorcism" in Raqqa, Syria, once a stronghold of the Islamic State.

The trial will continue on Monday and go through the summer.

The New York Times