IS widow charged over death of US hostage Kayla Mueller

The US has charged a widow of late Islamic State group financial leader Abu Sayyaf for her alleged role in the death of US aid worker Kayla Mueller, who is believed to have been killed nearly a year ago today.

Nisreen Assad Ibrahim Bahar, a 25-year-old known as Umm Sayyaf, was on Monday accused of conspiring to provide support to the militants and of forcibly imprisoning Mueller and other captives in the couple's home.

The complaint was brought by the Department of Justice and the FBI at US District Court in Virginia.

If convicted, Bahar, who is currently in Iraqi custody awaitng prosecution for terror-related activities, faces life in prison. 

Abu Sayyaf was killed in May 2015 in a US commando raid inside war-torn Syria. 

Bahar was captured during the operation, and US forces also rescued a young Yazidi woman and seized a stash of firearms, the complaint said.

In August, the White House said that Bahar would be prosecuted in Kurdish Iraq and “would be held accountable for her actions”.

Since Bahar's detention, reports have said that Mueller, 26, and the other women were subjected to violent sexual abuse while in captivity.

Bahar has acknowledged that IS leader Abu Bakr al-Baghdadi "owned" Mueller during her captivity and repeatedly sexually assaulted the American aid worker.

IS fighters claimed that Mueller, who was kidnapped in the Syrian city of Aleppo in August 2013, was killed in a February 2015 coalition air strike that buried her in rubble.

The US announced her death on 9 February 2015 but officials say the circumstances around her death remain unclear.

Syrian activists have said that IS sentenced her to death in 2015 after the US failed to release a high-ranking IS member.

Mueller and other captives "were at various times handcuffed, held in locked rooms and given orders on a daily basis with respect to their activities, movements and liberty", according to the complaint filed in Virginia.

"While in captivity, Kayla Jean Mueller was sexually abused by Baghdadi, who forced her to have sex with him," it added.

"The defendant knew how Ms Mueller was treated by Baghdadi when Ms Mueller was held against her will in the defendant's home."

According to accounts from other women released from captivity, Mueller would try to prevent them from being sexually assaulted by Baghdadi.

The complaint also alleged that Bahar told the captives that "she would kill them if they did not listen to her".

Bahar admitted that she had sole responsibility for holding the hostages captive while her husband travelled on IS business, and that Baghdadi and other members of the group would stay at the residence at times, according to the complaint. 

The US is supporting the prosecution of Bahar in Iraq, said the Department of Justice statement. "We fully support the Iraqi prosecution of Sayyaf [Bahar] and will continue to work with the authorities there to pursue our shared goal of holding Sayyaf accountable for her crimes," Assistant Attorney General John Carlin said.

"We will continue to pursue justice for Kayla and for all American victims of terrorism."