Saudi Arabia says it will pursue the death penalty for five suspects charged with ordering and carrying out the killing of the Saudi writer Jamal Khashoggi, in the latest effort to distance the country’s de facto ruler, Crown Prince Mohammed bin Salman, from the grisly murder.

The Saudi public prosecutor claimed Saudi agents, including the head of forensics at the national intelligence service and members of Prince Mohammed’s security detail, had orders to abduct Khashoggi but decided to kill him when he resisted.

The claim had been contradicted by an earlier Saudi finding that the murder was premeditated.

Prince Mohammed was not implicated in the murder, a spokesman for the prosecutor said.

An intelligence officer was responsible for ordering the murder, the public prosecutor’s office said, and Khashoggi was given a lethal injection after a struggle with the extradition team inside the consulate.

Turkey has been formally asked to hand over audio tapes that allegedly capture the journalist’s death, he added.

Hours later, the US Treasury said it was imposing sanctions against 17 alleged conspirators, in an announcement that appeared timed to support the Saudi version of events. The Trump administration has attempted to shield Prince Mohammed from blame, and sponsored the theory that “rogue actors” had carried out the plot without his knowledge.

Crown Prince Mohammed bin Salman: the Saudi public prosecutor said he had not been implicated in Jamal Kashoggi’s murder. Photograph: Reuters

The announcements follow growing international outcry over the killing of Khashoggi, a Washington Post columnist last seen entering the consulate on 2 October to obtain paperwork for his marriage.

Almost seven weeks later, who ordered the exiled journalist’s death remains central to the scandal. Turkey believes approval was given by Prince Mohammed himself, and has continued its efforts to isolate the designated heir to the throne through a damning drip-feed of evidence that has placed the conspiracy at the doors of the royal court.

On Thursday Turkey’s foreign minister, Mevlüt Çavuşoğlu, described the Saudi statement as insufficient and insisted the killing had been premeditated. “The necessary equipment and people were previously brought in to kill and later dismember him,” he said.

Saudi prosecutors say 21 of its officials have been indicted – including the 15-man hit team as well as crews alleged to have carried out reconnaissance before the murder.

Ankara and Riyadh have been conducting a joint investigation into Khashoggi’s death. However, Turkish officials accuse their Saudi counterparts of stonewalling on the whereabouts of his body, and sending a forensic team disguised as investigators, who, rather than investigating the murder, attempted to scrub the consulate of Khashoggi’s DNA.

Sheikh Shalan al-Shalan, Saudi Arabia’s deputy attorney general, claimed on Thursday that the murder was ordered by one man who had been tasked with kidnapping Khashoggi, rather than killing him. He said the kidnap attempt quickly turned violent “so he decided to kill him in the moment”.

The claim that the death was not premeditated is at odds with earlier versions of events endorsed by Saudi officials. Turkey says it has audio recordings that prove Khashoggi was strangled and then dismembered within minutes of entering the consulate. A search for his remains in a forest near Istanbul has been unsuccessful. However, biological evidence of the murder is understood to have been found at the nearby consul general’s residence.

Investigators are working on the assumption that a second phase of the murder operation was carried out in the garage of the official residence, where Khashoggi’s body parts were dissolved in acid and poured down drains and into a garden well.

Turkey is yet to publicly reveal full transcripts of the audio tapes it says depict the killing, or divulge how the recordings were made. However, they have been widely shared with allied intelligence agencies and even played to a Saudi agent, according to President Recep Tayyip Erdoğan, who is leading the diplomatic offensive against Prince Mohammed.

Erdoğan has said the order to murder Khashoggi came from the highest levels of the Saudi government. The former head of MI6, Sir John Sawers, has described Saudi claims that Prince Mohammed was unaware of the murder plot as “blatant fiction”.

The US, meanwhile, remains wedded to its ties with Prince Mohammed, whom it sees as a pivotal ally in the region both as a bulwark against Iran and an outreach to Israel. Trade ties are also central to the considerations of Donald Trump, whose son-in-law, Jared Kushner, has formed a close relationship with the crown prince.

On Thursday night Republican and Democratic US senators introduced legislation seeking to strike back at Riyadh over the killing and for its role in Yemen’s devastating civil war. If it were to become law, the bill would suspend weapon sales to Saudi Arabia and prohibit US refuelling of Saudi coalition aircraft. Senator Bob Menendez, the top Democrat on the Senate Foreign Relations Committee, said the sanctions announced earlier were not enough to ensure a credible investigation of Khashoggi’s death.

Global condemnation that has followed Khashoggi’s murder has diminished Prince Mohammed in the eyes of other international partners. The fallout poses the greatest threat to the kingdom since the 9/11 attacks, in which 15 of the 19 hijackers were Saudi citizens.

The US national security adviser, John Bolton, said earlier this week that nothing on the tapes incriminated the crown prince. Turkey has hinted that separate, as yet undisclosed material it is holding brings the killing to the doorstep of the royal court. Saud al-Qahtani, Prince Mohammed’s most influential domestic aide, has been forced to leave amid accusations of organising the hit squad against Khashoggi. The crown prince’s critics, and even some loyalists inside the kingdom, say it is inconceivable that such an operation could have been ordered without his authority.

Khashoggi had become an influential critic of some aspects of Prince Mohammed’s reform programme in the last 18 months of his life, during which he lived in exile mainly in Washington DC. An insider turned outsider, he had used his Washington Post column to pen pointed critiques and political observations that made him one of the Arab world’s most influential pundits.

He had been an advocate of political Islam, which is viewed by Saudi Arabia and the United Arab Emirates as a subversive threat, and had defied overtures from al-Qahtani to return to Riyadh.

Additional reporting by Bethan McKernan