US President Donald Trump has suggested Saudi Arabia’s Crown Prince could have been involved in the killing of journalist Jamal Khashoggi.

Trump labelled the kingdom’s response to the Washington Post columnist’s death as one of “the worst cover-ups ever”, adding that whoever is behind it “should be in big trouble”.

Speaking to the Wall Street Journal on Tuesday, Trump said he did not believe King Salman knew of the killing beforehand.

But asked if the powerful crown prince, also known as MbS, may have been involved, the president said: “Well, the prince is running things over there more so at this stage. He’s running things and so if anybody were going to be, it would be him.”

Members of the crown prince’s entourage, including close aide Maher Abdulaziz Mutreb, are alleged to be directly involved in the murder.

Trump added that he “really wanted to believe” the Saudi royal family’s claim that they were not associated with the crime.

Khashoggi was last seen entering the Saudi consulate in Istanbul on October 2, where he had gone to collect documents that would allow him to marry his fiancée, Hatice Cengiz.

Saudi Arabia has changed the story around his disappearance, first claiming that the critic of MbS left the building alone, before last week admitting that he was murdered in a “rogue operation”.

Claims by the Saudis that the journalist had died in a fist fight were previously described by Trump as “credible”.

The US is making small steps to punish the Saudis, but Trump has been reluctant to sanction the kingdom, which buys billions of dollars of US military equipment and has shares in major firms including Uber and Tesla.

Mike Pompeo, Secretary of State, announced on Tuesday that the US would be revoking visas of the 21 Saudi suspects, and they would no longer be eligible to enter the States.

“These penalties will not be the last word on this matter,” Pompeo added.

But Turkish officials say a 15-man team tortured, killed and dismembered the writer and say Saudi officials had planned the killing for days.

On Tuesday, President Recep Tayyip Erdogan told ruling party lawmakers in parliament that the murder was premeditated and “savage”.

Erdogan used the word “murder” no less than 15 times, and said the 18 people arrested in Saudi Arabia should be tried in Istanbul.

Turkish officials claim they have audio evidence that the 59-year-old, who moved to the US in a self-imposed exile more than a year before his death, was tortured.

MbS met with Jamal Khashoggi’s son in Riyadh on Tuesday.