Donald Trump, the US president, has criticised the rapidly mounting global condemnation of Saudi Arabia after a key Senate ally accused the kingdom’s crown prince of ordering the murder of missing journalist Jamal Khashoggi.

Lindsey Graham, the Republican senator and confidant of the US president, said he wanted to “sanction the hell out of Saudi Arabia” and pointed the finger at its crown prince, Mohammed bin Salman – known by his initials ‘MBS'.

"Nothing happens in Saudi Arabia without MBS knowing it," Mr Graham said, adding the crown prince was a "wrecking ball".

“He had [Mr Khashoggi] murdered in a consulate in Turkey and to expect me to ignore it - I feel used and abused," he said.

In an interview with The Associated Press, Mr Trump compared the situation to the allegations of sexual assault leveled against Supreme Court Justice Brett Kavanaugh during his confirmation hearing.

"I think we have to find out what happened first," he said. "Here we go again with, you know, you're guilty until proven innocent. I don't like that. We just went through that with Justice Kavanaugh and he was innocent all the way as far as I'm concerned."

Jamal Khashoggi at a press conference in 2014 credit: MOHAMMED AL-SHAIKH/AFP

Meanwhile, a Turkish forensic team allowed to search the Saudi consulate in Istanbul where Mr Khashoggi was last seen reportedly found “certain evidence” he had been killed there.

Mike Pompeo, the US secretary of state, met with Crown Prince Mohammed and his father, King Salman, during his visit to Saudi Arabia to investigate the disappearance.

Mr Khashoggi, who lived in America and wrote columns for The Washington Post, had become a leading critic of Crown Prince Mohammed – a powerful figure in the country – in recent years.

Crown Prince Mohammed played up US-Saudi ties, telling Mr Pompeo in front of reporters: "We are strong and old allies. We face our challenges together - the past, the day of, tomorrow.”

Images of the pair smiling and shaking hands put the Trump administration’s close relationship with Saudi leaders under the microscope after Mr Khashoggi’s disappearance.

Mr Trump’s first trip abroad as president was to Riyadh, the Saudi capital, and his administration has aligned itself with the country as it seeks to counter the threat posed by Iran.

Trump administration figures, in particular the president's son-in-law Jared Kushner, have also developed a close relationship with Crown Prince Mohammed.

Mohammed bin Salman, the Saudi crown prince credit: AFP PHOTO / FAYEZ NURELDINEFAYEZ NURELDINE/AFP/Getty Images

The 33-year-old has been touted as a progressive reformer but he is now under intense scrutiny.

US officials intercepted messages that reportedly suggest he ordered an operation to lure Mr Khashoggi back to Saudi Arabia, according to The Washington Post.

Mr Khashoggi was last seen walking into the Saudi consulate in Istanbul on October 2.

Turkish officials have claimed that 15 Saudi operatives, including one autopsy specialist carrying a bone saw, flew in and out of Istanbul on the day of Mr Khashoggi’s disappearance.

Mr Trump tweeted on Tuesday:

Mr Trump initially rejected calls for sanctions, saying he did not want to lose arms contracts worth $110 billion (£83 billion) with the Saudis. However he has also threatened “severe punishment”.

Turkish police spent nine hours searching the Saudi consulate on Tuesday amid reports that Saudi Arabia was preparing to admit that Mr Khashoggi had been killed but would say he died during a botched interrogation.

A Turkish official said that detectives had found clear evidence of Mr Khashoggi’s murder, according to the Associated Press, but did not say what was found. Recep Tayyip Erdogan, Turkey’s president, said the investigation was complicated because Saudi staff had painted over parts of the consulate in recent days.

“The investigation is looking into many things such as toxic materials and those materials being removed by painting them over,” Mr Erdogan said. He did not give more details.

Donald Trump initially expressed reluctance to sanction Saudi Arabia credit: AP Photo/Pablo Martinez Monsivais

Turkish detectives arrived late on Tuesday night at the residence of the Saudi consul-general, a short drive from the consulate, to continue the search.

CCTV footage shows a convoy of diplomatic vehicles drove from the consulate to the residence less than two hours after Mr Khashoggi disappeared. Some Turkish officials believe his body may have been hidden at the residence.

Turkish media said Mohammad al-Otaibi, the Saudi consul, left Turkey shortly before the police search at his home was due to begin.

Khalid bin Salman, the Saudi ambassador to Washington and younger brother of Crown Prince Mohammed, is being permanently recalled back to Riyadh, according to the New York Times.

Steve Mnuchin, the US treasury secretary, has said he still plans to attend the prince’s “Davos in the desert” summit next week but that he would make a final decision on Friday.

Foreign ministers from the Group of Seven called on Tuesday for a "transparent" probe into the disappearance of the journalist.

"We, the G7 foreign ministers, of Canada, France, Germany, Italy, Japan, the United Kingdom, the United States of America and the high representative of the European Union, affirm our commitment to defending freedom of expression and protection of a free press," read a statement.

"We remain very troubled by the disappearance of prominent Saudi journalist Jamal Khashoggi," added the statement by Canada, which currently holds the presidency of the group of industrial democracies.