Pressure is building on Saudi authorities to reveal the whereabouts of commentator and journalist Jamal Khashoggi, an outspoken critic of Crown Prince Mohammed bin Salman who disappeared this week in Istanbul after entering the Saudi Arabian consulate.

The Washington Post on Friday published a blank space where Khashoggi’s words would have been printed.

Thomas Friedman, a New York Times columnist who in November 2017 famously praised the Saudi crown prince’s reform program saying “only a fool would not root for it,” has now warned the young leader over Khashoggi’s disappearance.

“Saudi CP [crown prince] MBS and FM [foreign minister] al-Jubeir: You need to find/release my friend Jamal Khashoggi, who went missing in Saudi Istanbul consulate. It will be disastrous for your diplomacy if he’s been abducted,” Friedman tweeted Friday.

Hours later, Bloomberg published an exclusive interview with the crown prince, which touched on Khashoggi’s case.

Bin Salman dodged questions as to whether his critic faced charges in the kingdom, and said the disappearance was under investigation.

“My understanding is he entered [the consulate] and he got out after a few minutes or one hour. I’m not sure. We are investigating this through the foreign ministry to see exactly what happened at that time,” the crown prince said.

“He’s a Saudi citizen and we are very keen to know what happened to him. And we will continue our dialogue with the Turkish government to see what happened to Jamal there.

“We have nothing to hide,” he added, offering to allow Turkish authorities to search the Saudi consulate in Istanbul, where Khashoggi was last seen on Tuesday.

While the crown prince insisted Khashoggi had left the consulate, the Turkish-Arab Media Association told state news agency Anadolu that he had not been heard from since entering the building. Khashoggi’s Turkish fiancée told CNN he had never emerged and that she was waiting outside the gate the entire time.

Turkey’s Foreign Ministry on Wednesday summoned the Saudi ambassador to discuss the case, Anadolu reported citing diplomatic sources. Meanwhile, Turkish officials have remained tight-lipped about the incident.

Activists have expressed fears that Saudi authorities took the opportunity to detain the critic in Istanbul and extradite him to Saudi Arabia. It would not be the first such alleged case.

Loujain al-Hathloul, a leading advocate for women’s rights in the kingdom, was detained in the United Arab Emirates earlier this year and transported back to Saudi Arabia, according to fellow activists. In May, Saudi authorities arrested Hathloul along with six other women’s rights advocates.

Khashoggi at the time spoke up for Hathloul and openly criticized the wisdom of the crown prince’s moves, saying that the women’s rights activist should be “celebrated” rather than arrested.