US President Donald Trump has called Saudi Arabia’s response to the murder of journalist Jamal Khashoggi “the worst cover-up ever”.
He added that whoever organised the plot “should be in big trouble”.
Secretary of State Mike Pompeo said, shortly afterwards, that the US “will punish those responsible” and is revoking visas of 21 identified suspects.
The US has faced pressure to toughen its stance on Saudi Arabia, a key ally.
Speaking to reporters at the White House, Mr Trump said: “They had a very bad original concept, it was carried out poorly and the cover-up was the worst in the history of cover-ups.”
“Whoever thought of that idea, I think is in big trouble. And they should be in big trouble.”
The Saudi kingdom has provided conflicting accounts of what happened to Khashoggi, a US resident and Washington Post contributor. After weeks of maintaining he was still alive, the authorities now say the 59-year-old was murdered in a rogue operation after visiting the Saudi consulate in Turkey.
Mr Trump’s criticisms of Saudi officials are his strongest so far, but he has continued to highlight the kingdom’s importance as a US ally.
In a separate interview with the Wall Street Journal published late on Tuesday, Mr Trump addressed the possible involvement of senior Saudi royals in the killing and said he did not believe King Salman had prior knowledge of the crime.
When asked about the possible role of Crown Prince Mohammed bin Salman, the president replied: “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.”
He said he had questioned the crown prince about Khashoggi’s death, and been told he did not know about the operation when it was being planned.
Asked if he believed the royal family’s denial of any involvement in the killing, Mr Trump gave a long pause before saying: “I want to believe them, I really want to believe them,” the newspaper said.
Mr Trump also said US intelligence officials, including CIA director Gina Haspel, were returning from Turkey and Saudi Arabia with information about the case.
Secretary of State Mike Pompeo told reporters in Washington that he and the president were “not happy with the situation”.
In addition to revoking visas, Mr Pompeo said the US was looking into the possibility of imposing sanctions on those believed to be involved in Khashoggi’s killing.
“These penalties will not be the last word on this matter from the United States,” he added.
A State Department official told CNN that the suspects whose visas were being revoked would not be named due to “visa confidentiality”.
Earlier on Tuesday, Turkish President Recep Tayyip Erdogan told MPs from his ruling party that the killing of journalist Jamal Khashoggi was planned days in advance.
He said Turkey had strong evidence Khashoggi was killed in a premeditated and “savage” murder at the consulate in Istanbul on 2 October.
He also called for the suspects to be tried in Istanbul.
Mr Erdogan’s address coincided with the start of an investment conference in Saudi Arabia that has been overshadowed by the Khashoggi case. Dozens of government and business leaders have pulled out, but Crown Prince Mohammed bin Salman appeared at the event on Tuesday.
Many world leaders have condemned the murder of the prominent Saudi critic and demanded a full investigation.
King Salman chaired a cabinet meeting on Tuesday, after which a statement said that Saudi Arabia would hold to account those responsible for the killing, whoever they might be.
State media also said the king and the crown prince had held a meeting in Riyadh with members of the Khashoggi family, including Khashoggi’s son, Salah. The Associated Press has reported that Salah had been under a travel ban since last year because of his father’s work.
Saudi Arabia’s account of Khashoggi’s fate has not been consistent.
First it said Khashoggi had left the building alive, then that he had been killed in a “fist-fight” inside the consulate, before finally saying that Khashoggi had been murdered in a “rogue operation” that the leadership had not been aware of.
“The individuals who did this did this outside the scope of their authority,” Foreign Minister Adel al-Jubeir told Fox News. “There obviously was a tremendous mistake made, and what compounded the mistake was the attempt to try to cover up.”
He said that Saudi Arabia did not know where the body was.
An unnamed Saudi official told Reuters news agency on Sunday that Khashoggi had died in a chokehold after resisting attempts to return him to Saudi Arabia. His body was then rolled in a rug and given to a local “co-operator” to dispose of.
In addition to the arrests of 18 people, the Saudis say they have sacked two of the crown prince’s aides and set up an organisation, under his leadership, to reform the intelligence agency over the killing.
According to Reuters news agency, quoting Turkish and Arabic intelligence sources, one of the sacked aides appeared via Skype during Khashoggi’s questioning. Saud al-Qahtani was quoted as giving the instructions “bring me the head of the dog”, after the two men traded insults.
The sources say President Erdogan has a copy of the Skype audio but is refusing to hand it over to the US.