Donald Trump has said for the first time that Saudi crown prince Mohammed bin Salman could have been involved in the operation to kill the dissident journalist Jamal Khashoggi, noting that “the prince is running things over there” in Riyadh.

The comments, in an interview with the Wall Street Journal, appeared to mark a shift in the US president’s view of Khashoggi’s murder on 2 October in the Saudi consulate in Istanbul.

Trump has previously appeared to take Saudi royal denials of involvement at face value, but on a day the state department announced it would revoked the visas of Saudi officials implicated in the writer’s death, sanctions on Wednesday matched by the UK, he appeared to give the benefit of the doubt to King Salman but not necessarily to his powerful son.

Erdoğan’s Khashoggi speech poses tough questions for Bin Salman

Asked about the crown prince’s possible involvement, Trump 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.”

The interview was published as a pro-government Turkish newspaper said the director of the CIA, Gina Haspel, had been played audio and video evidence of Khashoggi’s torture and murder. The evidence was believed to be in the possession of Turkish intelligence officials.

Gina Haspel testifies at her Senate confirmation hearing.
Gina Haspel testifies at her May 2018 Senate confirmation hearing. Photograph: Chip Somodevilla/Getty Images
Haspel flew to Ankara on Monday night to assist Turkey’s investigation into Khashoggi’s death. Four sources familiar with the mission brief told Reuters she had asked to view the tapes.

While steadily coordinated leaks to media in the three weeks since Khashoggi’s disappearance strongly suggest there is audio and video evidence that contradicts the Saudi explanation of his death, there has been no official confirmation from the Turkish authorities.

In a speech to parliament the day of Haspel’s visit, in which Erdoğan had promised to deliver the “naked truth” about what happened to Khashoggi, he did not mention the existence of tapes.

During talks at Turkey’s National Intelligence Organisation (MIT) on Tuesday, officials tabled the evidence gathered so far, including audio and video recordings and findings from searches of the consulate building and consul general’s house, the pro-government Sabah newspaper said.

Trump told the Wall Street Journal that he had closely questioned Prince Mohammed about Khashoggi’s murder, posing questions repeatedly and “in a couple of different ways”.

“My first question to him was, ‘Did you know anything about it in terms of the initial planning?’ … Prince Mohammed replied that he didn’t,” Trump said.

“I said, ‘Where did it start?’ And he said it started at lower levels.” According to the Guardian source.

Asked whether he believed the denials, the president paused for several seconds. “I want to believe them. I really want to believe them,” he said.

Mohammed bin Salman meets Salah bin Jamal Khashoggi, son of Jamal Khashoggi.
Mohammed bin Salman meets Salah bin Jamal Khashoggi, son of Jamal Khashoggi. Photograph: Bandar Algaloud Handout/EPA
Trump has put out mixed messages over the case in the last few weeks, promising “very severe” consequences and mentioning possible economic sanctions, but also ruling out a block on arms sales to Saudi Arabia and highlighting the country’s role as a US ally against Iran and Islamist militants.

At the weekend, he said Saudi claims that Khashoggi had died in a fist fight were credible.

His remarks to the Wall Street Journal came as the state department announced that 21 Saudi nationals would have their US visas revoked or be made ineligible for US visas over the journalist’s killing.

Only an international court can bring Khashoggi’s killers to justice | Geoffrey Robertson

Mike Pompeo, the US secretary of state, said other measures were being considered, including sanctions: “These penalties will not be the last word on the matter from the United States.

“We’re making very clear that the United States does not tolerate this kind of ruthless action to silence Mr Khashoggi, a journalist, through violence,” Pompeo said. “Neither the president nor I am happy with this situation.”

Theresa May, speaking in the House of Commons on Wednesday, said she would also take action to prevent suspects entering the UK. “If these individuals currently have visas, those visas will be revoked today,” she told MPs.

The US visa revocations were the first punitive measures the Trump administration has taken against Saudi Arabia since Khashoggi disappeared. Under pressure from Congress, however, it is likely to extract a higher price from Riyadh for the killing of Khashoggi, a US resident and columnist for the Washington Post who was a critic of the crown prince.

Speaking to reporters in the Oval Office, Trump spoke contemptuously about the murder plot: “They had a very bad original concept. It was carried out poorly and the cover-up was one of the worst in the history of cover-ups.”

He returned to the theme of how the crime had been carried out at a dinner with military leaders: “They did a bad job of execution and they did a bad job of talking about it or covering it up,” he said.

“I’m saying they should have never thought about it. Once they thought about it, everything else they did was bad too … It should have never happened.”

Erdoğan’s publicly dismissed the Saudi version in his speech on Tuesday, making fresh allegations that Khashoggi’s “savage” and premeditated murder, and calling for an independent investigation