Jamal Khashoggi joins growing list of Saudi dissidents who have mysteriously disappeared in recent years

At least three other Saudi nationals related to royal family have been allegedly kidnapped

On Tuesday, Saudi dissident Jamal Khashoggi walked into his country's consulate in Istanbul. Turkish officials say he died there at the hands of a "murder squad" flown from Riyadh to kill him and dispose of his body.

Saudi Arabia has denied the accusations. But Khashoggi is not the first critic of the Saudi government to disappear under mysterious circumstances. In the last few years, at least three other Saudi nationals – all relatives of the royal family, all outspoken critics of Saudi leadership and all living in Europe – have been kidnapped. Friends and allies say they were thrown into prison in Saudi Arabia – or worse.

"Despite the denials, the oil-rich Kingdom is an absolute monarchy and has a track record of refusing to tolerate dissent by its citizens – both domestically and abroad," wrote Middle East Eye.

Here's what happened to those dissidents:

Sultan bin Turki

Sultan bin Turki, a Saudi prince living in Geneva, became an outspoken critic of the kingdom's leadership after he left the country in 2002.

Mr Sultan said he was invited to breakfast the next year by Abdulaziz bin Fahd, a son of then-Saudi ruler King Fahd. Over breakfast, Mr Abdulaziz asked Mr Sultan to return to Saudi Arabia to "resolve" some of his issues. He refused.

A couple of minutes later, Mr Abdulaziz stepped out to make a phone call. Then, Mr Sultan said, masked men surrounded him. They beat him, handcuffed him and plunged a needle into his neck. When Mr Sultan awoke, he said, he was on a plane back to Saudi Arabia.

Mr Sultan said he spent seven years in prison or under house arrest in Saudi Arabia before being granted permission to fly to Boston in 2010 for a medical procedure. While there, he filed a complaint in Swiss court accusing Mr Abdulaziz of kidnapping him, but little came of the case.

In 2016, he agreed to allow Saudi Arabia to fly him from Paris to Cairo to visit his father. Friends say Mr Sultan was assured that he would be safe. He was allowed to bring his medical team, along with Western bodyguards.

Instead, the plane took him to Riyadh. Witnesses say soldiers dragged Mr Sultan from the plane, where a team of armed guards gathered. He has not been allowed to leave the country since.

Turki bin Bandar

Turki bin Bandar was once a key member of the Saudi royal family's inner circle and the head of the royal family's security. But he fell out of favour after a bitter inheritance dispute and was jailed.

After his 2012 release, Mr Turki fled to Paris, where he began creating YouTube videos calling for reform in Saudi Arabia. When Ahmen al-Salem, then deputy minister of the interior, called Mr Turki and tried to persuade him to come home, Mr Turki recorded the call and posted the audio online.

In 2015, Mr Turki disappeared while on a business trip in Morocco. Wael al-Khalaf, a friend and blogger, told the BBC that he was told by a "senior officer in the kingdom" that Mr Turki was in Saudi Arabia. "They'd taken him, he'd been kidnapped," Mr Khalaf told the outlet.

"Someone gave Turki bin Bandar the impression Morocco was safe, so he went there to do some business," a member of a Saudi opposition group told The Guardian. "And the Moroccan government took him and gave him to the Saudis."

Saud bin Saif al-Nasr

In 2014, Saud bin Saif al-Nasr, a relatively minor royal with a penchant for gambling and glitzy hotels, began tweeting about the Saudi monarchy from the comfort of Italy. Mr Saud criticised the country's leaders on social media for supporting the overthrow of Egyptian President Mohamed Morsi. In September 2015, Mr Saud publicly praised an anonymous letter written by a Saudi prince calling for a coup to remove King Salman.

A few days later, his Twitter account went silent.

Prince Khaled bin Farhan, another dissident prince in Germany, told the BBC he believes Mr Saud was "tricked" into travelling from Milan to Rome on a private plane.

Mr Saud had been told a Russian-Italian company wanted to open branches in the Persian Gulf, but Mr Khaled said the whole story was made up by Saudi intelligence officials. "A private plane from the company came and took Prince Saud. But it didn't land in Rome, it landed in Riyadh," Mr Khaled told the BBC. "Now Prince Saud's fate is the same as Prince Turki's, which is prison ... The only fate is an underground prison."

The Washington Post