Isis: Who is Islamic State hostage Kayla Mueller?

A female US hostage, feared to have been killed by Islamic State, has been named as 26-year-old aid worker Kayla Mueller.

Several Isis-linked Twitter accounts have claimed that the American aid worker was killed in the bombing raid on the Syrian city of Raqqa early on Friday. (February 6)

An aid worker from the small town of Prescott in Arizona, Ms Mueller is known in her hometown for being an ardent human rights activist. As a teenager she campaigned on behalf of genocide victims and volunteered for three years with the Save Darfur Coalition. She was presented with several youth awards in recognition of her selfless dedication to human rights causes and subsequently committed her life to supporting humanitarian aid efforts overseas.

After graduating in 2009, she spent a year living and working with humanitarian aid groups in northern India, Israel and Palestine. Returning to Arizona in 2011, she worked at an AIDS clinic and volunteered at a women's shelter at night.

In 2012, observing the plight of the Syrian refugees, Mueller was moved to travel to the war-torn region to support the work in the refugee camps. Working with aid agencies including Support to Life and the Danish Refugee Council she helped refugees on the Turkish border. In 2013, she described how she helped reunite a six-year-old with his relative after the camp was bombed.

Speaking to Prescott's Daily Courier she said: "For as long as I live, I will not let this suffering be normal, (I will not let this be) something we just accept. This story is not rare in Syria," she added. "This is the reality for Syrians two and a half years on. "When Syrians hear I'm an American, they ask, 'Where is the world?' All I can do is cry with them, because I don't know."

Miss Mueller was reportedly taken hostage in August 2013 in Aleppo, Syria along with a number of Syrian aid workers, including her boyfriend, after leaving a Spanish Medicins Sans Frontieres hospital.

While the other aid workers were released IS demanded a $6.6m (£4.3m) ransom for Ms Mueller's freedom. She is believed to be Islamic State's last remaining American hostage.

Following reports that their daughter may have become the latest victim of the extremist Islamist group, her parents, Carl and Marsha Mueller, issued a statement on Friday describing Kayla's dedication to the people of Syria.

"Kayla moved to the Turkish/Syrian border in December 2012 and began working with the organizations Support to Life and the Danish Refugee Council to assist families who had been forced to flee their homes. Kayla found this work heartbreaking but compelling; she was extremely devoted to the people of Syria.

"When asked what kept her going in her mission, she said: 'I find God in the suffering eyes reflected in mine, if this is how you are revealed to me, this is how I will forever seek you.'"

Her parents, both in their early 60s, have a large detached home in a rural area of the state, where her father runs an auto body repair shop. Till now, they had kept their daughter's identity secret, fearing any publicity would put her in more danger.

The US State Department has not yet confirmed the identity of the American hostage killed in an air strike. If Miss Mueller's death is confirmed, she would be the fourth American to have been killed while being held hostage by the terrorist organisation.

American Journalists James Foley and Steven Sotloff, and aid worker Peter Kassig were also beheaded by the group.