Security camera footage was removed from the Saudi consulate in Istanbul and Turkish staff were abruptly told to take a holiday on the day the dissident journalist Jamal Khashoggi disappeared while inside the building, Turkish authorities have claimed.

A week after Khashoggi vanished in the heart of Turkey’s biggest city, details of the investigation into his disappearance continued to point towards Riyadh having ordered Khashoggi’s seizure.

Profile Who was Jamal Khashoggi? Show Hide Jamal Khashoggi was one of the Arab world’s most prominent journalists and commentators. He was an outspoken critic of Saudi Arabia who dared to defy Crown Prince Mohammed bin Salman. While living in Saudi Arabia, Khashoggi was told to stop writing or posting on Twitter, where he had more than 1.6 million followers. He moved to the US in June 2017, where he continued to comment on his country both in print and on television. He wrote columns for the Washington Post and the Guardian.

His message struck a nuanced tone in the US, where he tried to acknowledge the reforms undertaken by Bin Salman while also highlighting the flaws. Khashoggi previously had close links with the Saudi royal family, including having served as a media aide to Prince Turki al-Faisal, when the latter was director general of the Saudi intelligence agency. He was also a former editor of the Saudi newspaper al-Watan and had worked with Prince Alwaleed bin Talal, a grandson of the first Saudi king. Khashoggi was murdered in the Saudi Arabian consulate in Istanbul in October 2018. Photograph: Virginia Mayo/AP

Investigators believe the squad responsible for his disappearance from the Saudi consulate spent several hours at the nearby consul general’s house before leaving for the airport in a convoy of six cars, one of which is thought to have carried the missing dissident or his body.

A still-frame image emerged on Tuesday of Khashoggi striding towards the diplomatic mission before he disappeared. The black van that was allegedly used later to smuggle him away was parked next to the front door.

Details of the planes used to fly 15 Saudi officials from Riyadh to Istanbul have also been confirmed. Two corporate jets rented from a company frequently used by the Saudi government arrived in Istanbul on 2 October and left separately the same evening. One jet, with the tail registration HZ-SK1, left for Cairo, and the second, HZ-SK2, flew to Dubai. Flight tracking records show they both later continued to Riyadh. Turkish investigators believe the CCTV footage from inside the consulate was onboard.

A Turkish police team entered the consulate building on Tuesday after being given access by Saudi officials. Journalists had been allowed into the building on Saturday.

However, despite a circumstantial case being established that blames Saudi Arabia for Khashoggi’s abduction, there were signs that Turkish officials were unwilling to further incriminate the kingdom, with which Turkey has lucrative trade ties and attempts to maintain a delicate regional relationship.

Political leaders have not delivered on pledges to supply video footage that purports to show heavy bags being carried from the consul gate to the waiting cars. Officials who had offered glimpses into the investigation for the past week were no longer prepared to talk.

Yasin Aktay, an adviser to the Turkish president, Recep Tayyip Erdoğan, claimed “the Saudi state is not blamed here”, a marked shift in rhetoric that had earlier called for the kingdom to explain what had happened.

“We have our own problems with a deep state,” he told al-Araby in an interview. Earlier, Aktay had pointedly claimed that Khashoggi had been murdered by people sent from Riyadh.

In a further sign of an apparent climbdown, the pro-government newspaper Daily Sabah suggested that the focus of the investigation had moved towards the possibility that Khashoggi was smuggled alive on to one of the planes. Turkish officials had been adamant that the journalist was killed inside the consulate; a claim they repeated to US authorities who began asking questions about Khashoggi’s disappearance at the weekend.

Privately, senior officials have told counterparts in the US and Europe that they still believe Khashoggi was killed, but that political leaders are willing to make a climbdown for Riyadh in return for concessions.

The spectre of a political dimension to the investigation has raised the prospect that evidence that could establish Khashoggi’s fate may never be disclosed.

The disappearance of the acclaimed columnist and senior adviser to previous Saudi regimes has rocked Washington, where he had been based for the past year as a columnist for the Washington Post, and struck fear through establishment circles in Riyadh, where the 59-year-old had been a popular figure. He was one of the few public intellectuals to openly critique the new administration of the crown prince, and heir to the throne, Mohammed bin Salman.

On Tuesday, his fiancee, Hatice Cengiz, used an opinion piece for the newspaper to appeal to Donald Trump for help “shed light” on the disappearance. “I also urge Saudi Arabia, especially King Salman and Crown Prince Mohammed bin Salman, to show the same level of sensitivity and release CCTV footage from the consulate,” Cengiz wrote.

Saudi journalist Jamal Khashoggi criticised the regime – and paid with his life | David Hearst Read more

Erdoğan, who is returning from a visit to Budapest, has insisted he is personally interested in the case and has demanded a transparent inquiry. US officials told the Guardian that Turkey had earlier put the evidence it had gathered directly to Saudi officials and had authorised a series of state-sanctioned leaks intended to pressure Riyadh when those officials had refused to respond.

The change in tone from Ankara would suggest that attitudes had also shifted in Riyadh, which has strenuously denied any role in Khashoggi’s disappearance and insisted he walked freely from the consulate, which he had attended to sign divorce papers to allow him to marry his Turkish fiancée.

“The Turks need to continue to be transparent about this,” a senior US official told the Guardian. “They have the Saudis in a delicate position here and know more than they’re letting on. This matters to the current administration. This guy can’t be allowed to vanish.”

Britain, France and the EU have also called for an urgent, credible investigation.