Jamal Khashoggi, the prominent Saudi journalist missing since he entered his country's consulate in Istanbul on October 2, has been an outspoken critic of the ultra-conservative kingdom's government.
Turkish police believe that the Washington Post contributor, who went into self-imposed exile in the United States in 2017 after falling out with Crown Prince Mohammed bin Salman, was murdered inside the consulate, according to an unnamed Turkish government official, a claim strongly denied by Riyadh.
Prince Mohammed has invited police to inspect the consulate, stressing his country had "nothing to hide".
Never one to mince his words, Khashoggi described a new Saudi era of "fear, intimidation, arrests and public shaming" in an article published in the Post last year.
He had previously served as an advisor to the Saudi government, but Khashoggi, who turns 60 on October 13, has been a vociferous critic of Prince Mohammed's policies in both the Arab and Western press.
In a March 6 editorial in Britain's The Guardian newspaper co-authored with Robert Lacey, Khashoggi wrote: "For his domestic reform programme, the crown prince deserves praise. But at the same time, the brash and abrasive young innovator has not encouraged or permitted any popular debate" on the changes.
"He appears to be moving the country from old-time religious extremism to his own 'You-must-accept-my-reform' extremism, without any consultation -- accompanied by arrests and the disappearance of his critics."
Khashoggi fled the country in September 2017, months after Prince Mohammed was appointed heir to the throne and amid a campaign that saw dozens of dissidents arrested, including intellectuals and Islamic preachers.
Khashoggi said he had been banned from writing in the pan-Arab daily Al-Hayat, owned by Saudi Prince Khaled bin Sultan al-Saud, over his defence of the Muslim Brotherhood which Riyadh has blacklisted as a terrorist organisation.
The writer said Saudi authorities banned him from using his verified Twitter account after he said the country should be "rightfully nervous about a Trump presidency".
US President Donald Trump has expressed support for Crown Prince Mohammed.
Khashoggi has also criticised Saudi Arabia's role in Yemen, where Riyadh leads a military coalition fighting alongside the government in its war with Iran-backed rebels.
The writer opposes a Saudi-led boycott of Qatar, a tiny Gulf emirate that has found itself isolated over its allegedly close ties to extremist groups and Iran.
Khashoggi was born in the western Saudi city of Medina, revered in Islam as the burial place of the Prophet Mohammed.
He has done business with billionaire Saudi Prince Al-Waleed bin Talal.
After a youth spent studying Islamic ideology, Khashoggi later embraced more liberal ideas.
He began his career as a journalist with Saudi dailies in the 1980s, covering the Afghanistan conflict for the Saudi press.
Authorities came to see Khashoggi as too progressive and he was forced to resign as editor-in-chief of the Saudi daily Al-Watan in 2003.
Khashoggi has retained ambiguous ties to Saudi authorities, having held advisory positions in Riyadh and Washington, including to Prince Turki al-Faisal, who ran Saudi Arabia's intelligence agency for more than 20 years.