Tributes have been paid to a British journalist and student who died in Istanbul, as friends called into question the circumstances of her death.
Jacqueline Anne Sutton, known as Jacky, is reported to have died at the airport in the Turkish city.
The 50-year-old held various positions over the years with humanitarian organisations and the United Nations as well as working as a producer for the BBC, according to her LinkedIn profile.
Ms Sutton, who spoke five languages including basic Arabic, had been studying for a PhD at the Centre for Arab and Islamic Studies at the Australian National University.
Her research was on international development support to female media professionals in Iraq and Afghanistan between 2003 and 2013 and she had been carrying out field work in Erbil, Iraq, since July.
Centre director Professor Amin Saikal said people at the university are "deeply saddened and shocked by the tragic death of one of its brilliant PhD students".
Prof Saikal added: "She was not only an outstanding research scholar, but a highly valued friend and colleague who made remarkable contributions to the work and activities of the centre."
She was reported to be the acting Iraq director for the Institute for War and Peace Reporting (IWPR) at the time of her death.
Friends of Ms Sutton have questioned reports by Turkish media outlets that she killed herself after missing a connecting flight and admitting she did not have enough money to pay for another ticket.
She is reported to have arrived at Ataturk Airport from London on Saturday night.
Journalist and international development worker Rebecca Cooke called for an international investigation. She said: "Shocking and sad news about the death of Jacky Sutton in Istanbul. An international not just local investigation is needed."
Julia Shaw called the news "unbelievable".
She tweeted: "Jacky Sutton you will be dearly missed. Unbelievable news."
Sudipto Mukerjee, a country director with the United Nations Development Programme, wrote: "Very difficult to believe that my colleague @undpiniraq staffer and seasoned traveler @JackySutton committed suicide."
Lebanon-based Jessica Dheere said she was devastated at the news, which comes after the death of the IWPR's director Ammar Al Shahbander, who was killed in a car bomb attack in Baghdad in May.
She tweeted: "Incredibly distraught about death of 2nd #IWPR #IRAQ director in 6 mths. #RIP Jacky Sutton. U were a force."
The Foreign Office confirmed it is providing consular assistance to Ms Sutton's family.