Saudi journalist Jamal Khashoggi disappeared almost two weeks ago while on a visit to the Saudi Consulate in Istanbul.
His disappearance has sparked an international uproar involving the kingdom, Turkey and the United States that remains unresolved.
Mr Khashoggi - a Washington Post contributor - had written columns critical of Saudi Crown Prince Mohammed bin Salman, the kingdom’s war in Yemen and its crackdown on activists and businessmen.
Turkish officials say they fear a team of Saudi agents killed and dismembered Mr Khashoggi, and they have released surveillance footage of the alleged perpetrators and mysterious movements outside the consulate on October 2, the day he entered.
The kingdom says the allegations are “baseless” but has offered no evidence Mr Khashoggi ever left the consulate.
Here is a look at what we know about the disappearance.
Who is Jamal Khashoggi?
Mr Khashoggi is a long-time Saudi journalist, foreign correspondent, editor and columnist whose work has been controversial in the past in the ultra-conservative Sunni kingdom. He went into self-imposed exile in the United States following the ascension of Prince Mohammed, now next in line to succeed his father, the 82-year-old King Salman.
Mr Khashoggi was known for his interviews and travels with Osama bin Laden between 1987 and 1995, including in Afghanistan, where he wrote about the battle against the Soviet occupation. In the early 1990s, he tried to persuade bin Laden to reconcile with the Saudi royal family and return home from his base in Sudan, but the al-Qaida leader refused.
Mr Khashoggi maintained ties with Saudi elites and was viewed as a link between the West and the often opaque royal court. As a contributor to the Post, Mr Khashoggi has written extensively about Saudi Arabia, including criticising its war in Yemen, its recent diplomatic spat with Canada and its arrest of women’s rights activists after the lifting of a ban on women driving.
What happened to him?
Mr Khashoggi, whose 60th birthday was on Saturday, went to the Saudi Consulate in Istanbul’s 4th Levent neighbourhood on September 28 seeking documents so he could be married to his Turkish fiancee, Hatice Cengiz. He was told to return to the consulate on October 2 to pick up those documents, Ms Cengiz says.
Surveillance footage later aired on Turkish state television shows Mr Khashoggi walking into the consulate at 1.14pm on October 2. A little less than two hours later, surveillance footage shows several vehicles with diplomatic licence plates move from the consulate to the consul’s home some 1.2 miles away.
Ms Cengiz, who spent hours waiting for Mr Khashoggi outside while holding his mobile phones, says her fiance never walked out of the consulate to meet her. Surveillance footage shows her pacing around outside at 5.33pm, speaking on her phone. No footage made public so far has shown Mr Khashoggi walking out of the consulate.
What is Turkey saying?
Turkish officials, speaking on condition of anonymity to discuss the investigation, say they fear Saudi Arabia killed Mr Khashoggi. They claim they have audio and video recordings of Mr Khashoggi being interrogated, killed and dismembered. However, no such recordings have been released publicly so far.
Turkish security officials, rather than holding news conferences, have leaked information through pro-government media. Newspapers published the names and photographs of 15 Saudi men in the country’s military and security services who are said to have formed an “assassination squad” sent to target Mr Khashoggi. Turkish officials told The Associated Press one of those men was a post-mortem expert.
Turkish media have also released a series of videos, apparently taken from surveillance cameras, showing the alleged Saudi agents arriving on private jets the day Mr Khashoggi disappeared, checking into and out of hotels near the consulate, and then flying out that night.
A Turkish newspaper also claimed that Mr Khashoggi’s Apple Watch recorded audio of his murder and transmitted it to his iPhone outside the consulate and to his iCloud account. However, the newspaper did not explain how the alleged recording was transmitted and included a claim that Mr Khashoggi’s assailants used his finger to unlock it when such watches do not have fingerprint ID scanners.
Turkish officials have not responded to questions from the AP about Mr Khashoggi’s Apple Watch. Analysts have suggested Turkey may be trying to protect its intelligence-gathering methods by leaking information this way.
What is Saudi Arabia saying?
Saudi Arabia has offered no explanation for how the writer could have left the consulate and disappeared into Istanbul as his fiancee stood outside waiting for him.
Early on Saturday, Saudi interior minister Prince Abdulaziz bin Saud said: “What has been circulating in terms of supposed orders to kill him are outright lies and baseless allegations against the kingdom’s government.”
Meanwhile, Saudi media has tried to blame the crisis on Qatar, which the kingdom and three other Arab nations now boycott as part of a bitter political dispute, without offering proof of that country’s involvement. The Qatar-funded satellite network Al-Jazeera has extensively focused on Mr Khashoggi’s disappearance over the last week.
A Saudi-owned satellite news channel, meanwhile, has begun referring to the alleged 15-man team as “tourists”, without providing evidence to support the claim.
What is the US saying?
President Donald Trump spoken to King Salman about Mr Khashoggi on Monday and told reporters: "He didn't really know. Maybe I don't want to get into his mind, but it sounded to me like maybe these could have been rogue killers - who knows?
"I have asked Secretary of State Mike Pompeo to get on a plane and go to Saudi Arabia... go to Turkey if necessary."
Mr Trump has previously threatened “severe punishment” if authorities determine Saudi Arabia was behind Mr Khashoggi’s disappearance.
But, he has also said he wants to maintain the arms deals he struck with the kingdom on a trip to Riyadh.
Meanwhile, American politicians are threatening to sanction individual Saudi officials if evidence links them to the writer’s disappearance.
What happens next?
A Saudi team has arrived in Turkey to investigate Mr Khashoggi’s disappearance. Meanwhile, Turkey has said it will search the Saudi Consulate for evidence, but that has yet to happen.
Turkey’s foreign minister Mevlut Cavusoglu said on Saturday Saudi Arabia had not yet co-operated with Turkey on the search for Mr Khashoggi. That could force Turkey’s hand in leaking more information about the case to pressure the kingdom to co-operate.