Turkey has not identified the nationality of either detainee but Turkish state broadcaster TRT's Arabic service said both were Palestinians and carried Palestinian passports.
A man held by Turkey on suspicion of spying for the United Arab Emirates has committed suicide by hanging himself in prison, the Istanbul prosecutor's office said Monday.
The suspect, named as Zaki Y. M. Hasan, was found hanging from the bathroom door in his one-person cell in Silivri prison, west of Istanbul, when guards arrived to give him food on Sunday morning, the prosecutor's office statement said.
It said the man had been registered in a roll-call that morning. An investigation has been launched and the Istanbul forensics institute has carried out an autopsy, the statement added.
The dead man was one of two suspects charged with international, political and military espionage. The pair were arrested on April 19 and had confessed to spying on Arab nationals, a senior Turkish official said at the time.
Investigators are examining whether the arrival in Turkey of one of the detainees was related to the murder of Saudi journalist Jamal Khashoggi six months ago.
The United Arab Emirates is a close ally of Saudi Arabia. Relations with Turkey have been strained since the two Arab states launched a blockade of their Gulf neighbor, Qatar, in 2017, while Ankara supported Doha.
Saudi Arabia and the UAE also view Turkish President Tayyip Erdogan's Islamist-rooted ruling AK Party as a supporter of groups like the Muslim Brotherhood, which they oppose.
Turkey has not identified the nationality of either detainee but Turkish state broadcaster TRT's Arabic service said both were Palestinians and carried Palestinian passports. Hasan was a 55-year-old retired major general and a senior intelligence official, TRT said on its website.
In an interview with Saudi-owned Al-Arabiya TV, a man who identified himself as Hasan's son said his father had gone to Turkey to search for a job and the family had lost contact with him on April 7.
"We were surprised that he was suddenly arrested after the false accusations against him," the son Youssef said.
He said he wanted Hasan's body sent home and urged Palestinian President Mahmoud Abbas and world powers to investigate his father's death.
"I want the creation of a specialized medical committee, including a trusted Palestinian doctor who can go there and do the autopsy on my father’s corpse in order to find the truth himself," he said.
A woman who identified herself as Hasan's sister in the same interview said she was certain her brother would not have committed suicide.
Khashoggi, a Washington Post columnist and critic of Saudi Crown Prince Mohammed bin Salman, was killed in the Saudi consulate in Istanbul on Oct. 2 by a team of Saudi operatives, provoking an international outcry.
According to the senior Turkish official, one of the two men arrived in Turkey in October, days after Khashoggi was killed, while the other arrived later to help his colleague.
The CIA and some Western countries believe the Crown Prince, Saudi Arabia's de facto ruler, ordered the killing, which Saudi officials deny. The Saudi public prosecutor has indicted 11 unidentified suspects on charges of ordering and committing the crime, including five who could face the death penalty.
Erdogan has urged the United States to put its weight behind the investigation into the Khashoggi killing and not to set the matter aside because of its ties with Riyadh.