Donald Trump has said US investigators are looking into how Jamal Khashoggi vanished at the Saudi consulate in Istanbul, as reports in the US implicated the powerful crown prince, Mohammed bin Salman, in plans to abduct the dissident journalist.

The US president suggested that even if Riyadh were directly implicated in Mr Khashoggi’s abduction or murder, it would not affect vast US arms sales to Saudi Arabia.

But senior Republicans in Congress have signalled they were prepared to force the US to take punitive action if Mr Khashoggi was found to have been murdered by the Saudi regime.

“We’re being very tough. And we have investigators over there and we’re working with Turkey, and frankly we’re working with Saudi Arabia. We want to find out what happened,” Mr Trump told Fox News on Thursday morning. The US state department had referred earlier questions about the case to the FBI.

Asked later on Thursday whether the US would cut arms sales if the Saudi government was found to be responsible for Mr Khashoggi’s disappearance, the president demurred, saying the US could lose its share of the huge Saudi arms market to Russia or China.

In the Oval Office Mr Trump pointed out that the disappearance took place in Turkey and that Mr Khashoggi was not a US citizen. On being told that the journalist was a US permanent resident, the president said: “We don’t like it even a little bit. But whether or not we should stop $110 billion from being spent in this country – knowing they have . . . two very good alternatives. That would not be acceptable to me.”

The president’s desire to protect weapons sales and his family’s close relationship with the Saudi monarchy could lead to a clash with congressional Republicans, some of whom are already uneasy about the high civilian death toll from the Saudi aerial bombardment of Yemen, using US-made bombs.

The Republican chair of the Senate foreign relations committee, Bob Corker, one of a handful of senators briefed on US intelligence on the case, said he believed Mr Khashoggi was murdered and that the “intel points directly” at the Saudi government. “I think they did it and unfortunately I think he is deceased. But they certainly could produce him and change the narrative,” Mr Corker told CNN.

The senator told MSNBC that he had looked at intelligence at a secure room at the Senate, and concluded: “It does appear that he’s been murdered, and I think over the next several days, things are going to become much clearer.”

Investigation

Mr Corker and 21 other senators sent a formal letter to the president triggering a mandatory US investigation into Mr Khashoggi’s fate. Under the Global Magnitsky Human Rights Accountability Act, the administration would have to report on the conclusions of the investigation and a decision on sanctions against the perpetrators.

The bipartisan support for strong action is putting pressure on the Trump administration, which is seeking to protect its close relationship with the Saudi monarchy.

On Thursday, a Turkish presidential aide, Ibrahim Kalin, said there would be a joint Turkish-Saudi investigation into the Khashoggi case.

Turkish officials have released a relentless drip-feed of information about an alleged crime that has shattered diplomatic norms and rocked Ankara and Riyadh. A report in the Washington Post, citing US intelligence sources, said Crown Prince Bin Salman had earlier authorised an operation to lure Mr Khashoggi back to Saudi Arabia and detain him.

The Turkish president, Recep Tayyip Erdogan, has challenged Saudi Arabia to provide CCTV images to back up its claims Mr Khashoggi had left the consulate safely, indicating he did not find the current Saudi explanations sufficient.

Britain’s foreign secretary said Saudi Arabia faced “serious consequences” if the suspicions of Turkish officials that Mr Khashoggi was murdered turned out to be true.

“If these allegations are true, there will be serious consequences because our friendships and our partnerships are based on shared values,” Jeremy Hunt told Agence France-Presse.

There are signs that Mr Khashoggi’s disappearance could have a lasting impact on global perceptions of the new Saudi leadership.

Turkey remains adamant that Mr Khashoggi was killed soon after he entered the consulate last Tuesday by a hit squad of 15 assassins who had flown in from Riyadh that day. Accounts of his apparent death have been widely circulated by officials, who have released the names of the Saudi citizens who arrived on two private jets; all were connected to state security agencies.

Turkish officials told the Middle East Eye website that Mr Khashoggi was ushered to the consul general’s office when he entered the consulate, then quickly seized by two men. “We know when Jamal was killed, in which room he was killed and where the body was taken to be dismembered,” the official said. “If the forensic team are allowed in, they know exactly where to go.”

Forensics

Riyadh had previously pledged to allow Turkish officials into the consulate, which is considered sovereign Saudi territory under international convention. However, access was rescinded after the names of the alleged assassins were revealed. Among the group, according to a passenger manifest supplied by Turkish authorities, was the head of forensics for the Saudi General Intelligence Presidency.

While investigators believe Mr Khashoggi was killed inside the consulate, suspicion about where his body may have been disposed of continues to focus on the Saudi consul general’s home, about 500 metres away. The building has an underground garage, and cars that were seen leaving the nearby building are believed to have spent several hours in the garage before leaving for Atatürk airport in Istanbul.

Officials also told Reuters they were examining data from an Apple Watch that Mr Khashoggi was wearing when he entered the building. Central to the investigation is whether data from the smartwatch could have been transmitted to a cloud, or his personal phone, which was with his fiancee, Hatice Cengiz, who was waiting outside.

Saudi officials had refused to engage with their Turkish counterparts until Tuesday, a source told the Guardian. Riyadh had used Washington as a conduit. “They have been behaving very strangely,” said an official. “It’s like they don’t care about the consequences. Is this incompetence, or arrogance? We really don’t know.” – Guardian