Turkish President Recep Tayyip Erdogan on Sunday said he was awaiting the results of an investigation into the disappearance of a Saudi journalist who a government source said was killed at Riyadh's consulate in Istanbul.

Washington Post contributor Jamal Khashoggi, 59, vanished after an appointment with Saudi officials on Tuesday.

A Turkish government source told AFP that police believed Khashoggi was killed at the Istanbul consulate, which Riyadh strongly denied.

Khashoggi had gone to the consulate to obtain documents needed to marry his Turkish fiancee.

Erdogan said he would wait for the outcome of the current investigation before taking a decision.

“I am following the (issue) and we will inform the world whatever the outcome” of the official probe, the president told reporters in Ankara.

“We hope to have results very quickly,” he added. “I am waiting, with high hopes.”

He said police were examining CCTV footage of entrances and exits at the consulate and Istanbul airport.

Police said earlier that around 15 Saudis, including officials, arrived in Istanbul on two flights on Tuesday and were at the consulate at the same time as Khashoggi.

“Based on their initial findings, the police believe that the journalist was killed by a team especially sent to Istanbul and who left the same day,” the government source told AFP on Saturday.

The journalist went to the building but “did not come back out”, police were quoted as saying by Turkey's state-run Anadolu news agency.

'Baseless' claims

The consulate rejected the claims that the journalist was killed there as “baseless”, in a Twitter message.

It said a Saudi team was in Turkey to investigate the disappearance.

The journalist's fiancee, Hatice Cengiz, said on Twitter she was “waiting for an official confirmation from the Turkish government” before she could believe the claims.

Khashoggi has been critical of some of Saudi Crown Prince Mohammed bin Salman's policies and Riyadh's intervention in the war in Yemen.

His criticisms appeared in both the Arab and Western press.

The former government adviser, who turns 60 on October 13, has lived in the United States since last year to avoid possible arrest.

Yasin Aktay, an official in Turkey's ruling Justice and Development Party (AKP) who was close to the journalist, said Khashoggi had made an appointment in advance with the consulate and called to check the documents were ready.

“His friends had warned him, 'Don't go there, it is not safe,' but he said they could not do anything to him in Turkey,” said Aktay.

He added that he still hoped the reports of his friend's death were untrue.

'Assault on press freedom'

Prince Mohammed said in an interview published by Bloomberg on Friday that the journalist had left the consulate and Turkish authorities could search the building, which is Saudi sovereign territory.

Turkey's foreign ministry on Wednesday summoned Saudi Arabia's ambassador over the issue.

Reporters Without Borders (RSF) said on Twitter that if reports of his death were confirmed, “this would constitute a horrific, utterly deplorable, and absolutely unacceptable assault on press freedom”.

Fred Hiatt, the director of the Washington Post's editorial page, said if the reports were true “it is a monstrous and unfathomable act”.

“Jamal was — or, as we hope, is — a committed, courageous journalist. He writes out of a sense of love for his country and deep faith in human dignity and freedom,” Hiatt said in a statement on the US newspaper's website.

A European Commission spokesperson said in a statement that Brussels was “closely” following the case, adding it was “awaiting clarifications from the Saudi authorities on the fate of Mr Khashoggi.”

Fled in 2017

Khashoggi fled from Saudi Arabia in September 2017, months after Prince Mohammed was appointed heir to the throne.

The journalist said he had been banned from writing in the pan-Arab Al-Hayat newspaper, owned by Saudi prince Khaled bin Sultan al-Saud, over his defence of the Muslim Brotherhood which Riyadh has blacklisted as a terrorist organisation.

He has also criticised Saudi Arabia's role in Yemen, where Riyadh leads a military coalition fighting alongside the government in its war with Iran-backed rebels.

Saudi Arabia, which ranks 169th out of 180 on RSF's World Press Freedom Index, has launched a modernisation campaign since Prince Mohammed's appointment as heir to the throne.

The ultra-conservative kingdom in June lifted a ban on women driving, but it has drawn heavy criticism for its handling of dissent.

Dozens of dissidents have been arrested including intellectuals and Islamic preachers.