Turkish authorities have claimed that the high-profile dissident Jamal Khashoggi was murdered in the Saudi Consulate in Istanbul by a hit squad sent from Riyadh, amid calls for an international inquiry into a disappearance that has rocked the region.

After alleging on Saturday that the journalist was killed in an act of state-sponsored murder, and that his body was later removed, officials said on Sunday they had based their beliefs on an investigation by police and intelligence officers, who had pored over security camera footage and spoken with informants inside the consulate.

Khashoggi: case against Saudi agents reverberates through Ankara and Riyadh Read more

The Turkish president, Recep Tayyip Erdoğan, struck a cautious note on Sunday, claiming he was “saddened” by Khashoggi’s disappearance and was waiting for the results of the investigation. Erdoğan’s tone appeared designed to delay a diplomatic crisis that would be likely to follow if and when he put his full authority to the allegations.

Earlier, an adviser to Erdoğan, Yasin Aktay, told Turkish CNN: “There is concrete information; it will not remain an unsolved case. If they consider Turkey to be as it was in the 1990s, they are mistaken.”

Officials from across the Turkish security apparatus continued to drip-feed information that alleged a pre-meditated murder had taken place of the dissident – a columnist and commentator who had pointedly criticised the Kingdom’s new crown prince, Mohammed bin Salman, and aspects of his reform programme.

Facebook Twitter Pinterest Saudi officials outside the consulate in Istanbul on Sunday. Photograph: Erdem Şahin/EPA

Investigators have made no claims about where Khashoggi’s remains may be, and some police units continue to believe there is not enough evidence to state authoritatively that the 59-year-old is dead. But all say he was at the very least abducted in a brazen state kidnapping that is likely to have broad implications in Turkey and beyond.

Central to the accusations against Riyadh are the arrival of 15 Saudi officials in Istanbul last Saturday, whom Turkey alleges were responsible for Khashoggi’s abduction and killing. Authorities in Riyadh have acknowledged dispatching a “security delegation” to Turkey but said they had no connection to the disappearance of Khashoggi, who was last seen entering the Saudi consulate in suburban Istanbul on Tuesday afternoon.

Saudi officials have strongly denied playing a role in the disappearance. The consulate released a statement that “strongly denounced these baseless allegations” and denied the Turkish claims had come from informed officials.

Investigators have examined five days of security camera footage that captured all those entering and leaving both entrances to the consulate. Their attention was drawn to men from inside the building moving boxes to a black car in the hours after Khashoggi vanished.

Friends of the Saudi writer, who had recently written extensively for the Washington Post, say he had sought assurances of safety from Saudi officials and had reluctantly entered the building to sign paperwork needed to marry his Turkish fiancee, Hatice Cengiz, the following day.

Khashoggi had remained in self-imposed exile in Washington for the past year, where he maintained close ties with former and current US officials, including some members of the Trump administration. There has been no immediate reaction from the US president, who has cultivated close connections to Prince Mohammed.

Human Rights Watch called for international investigators to be included in a transparent investigation.

“Given Saudi’s abuse of its diplomatic privileges – and all norms of diplomatic order – by brazenly kidnapping someone and allegedly killing him in their consulate, there should be a global demand for an international investigation into what happened,” said Sarah Leah Whitson, HRW’s executive director Middle East and North Africa. “This shouldn’t be left in the hands of Saudi or Turkey.

“Khashoggi’s reported kidnapping and even murder in the safe confines of the Saudi consulate is a deliberate strategy to sow fear into every Saudi who has spoken out about the government’s shortcomings, no matter how modestly or gently. The Saudi government wants them to know they are not safe inside or outside Saudi, and that no law or government can protect them.”