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,” he said.
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 killed in a rogue operation after visiting the Saudi consulate in Turkey.
In a news conference at the State Department in Washington, Mr Pompeo said that he and the president were “not happy with the situation”.
“We’re making very clear that the United States does not tolerate this ruthless action to silence Khashoggi, a journalist, through violence,” he said.
When asked whether the US would accept Saudi Crown Prince Mohammed bin Salman’s explanation of the incident, Mr Pompeo said: “We’re going to accept what America learns.”
“We have people working all across the world to put our own understanding together. We have to develop our own data set. We will learn the facts ourselves.”
Mr Pompeo also said the US was looking into the possibility of imposing sanctions on those believed to be involved in Khashoggi’s killing.
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.
While Mr Trump has ramped up his criticisms of Saudi officials, he has also highlighted the kingdom’s importance as a US ally.
Mr Trump had initially suggested that Khashoggi may have been murdered by “rogue” actors and at one point said that Saudi Arabia was being treated as “guilty until proven innocent”. He later said he was “not satisfied” with the Saudi version of events.
CIA director Gina Haspel has been sent to Turkey to review the matter.
Where do the Saudis stand?
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.
Media caption Jamal Khashoggi and how Saudi critics keep going missing
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.