Saudi Arabia says that journalist Jamal Khashoggi was murdered, blaming a "rogue operation" for a killing that sparked an international outcry.
Foreign Minister Adel al-Jubeir told Fox News the act had been a "tremendous mistake" and denied the powerful crown prince had ordered the killing.
The journalist was last seen entering the Saudi consulate in Istanbul.
The Saudis, under intense pressure to explain the journalist's whereabouts, have offered conflicting accounts.
They initially said he had left the building unharmed on 2 October but on Friday admitted for the first time he was dead, saying that he had been killed in a fight. This claim met widespread scepticism.
Turkish officials believe Mr Khashoggi, a prominent critic of the Saudi government, was murdered by a team of Saudi agents inside the building and say they have evidence to prove it.
How has the Saudi version of events changed?
Adel al-Jubeir's comments, describing the incident as murder, are some of the most direct to come from a Saudi official.
"We are determined to find out all the facts and we are determined to punish those who are responsible for this murder," he said.
"The individuals who did this did this outside the scope of their authority," he added. "There obviously was a tremendous mistake made, and what compounded the mistake was the attempt to try to cover up."
He also said that they did not know where the body was and insisted the action had not been ordered by Crown Prince Mohammed bin Salman, seen as Saudi Arabia's most powerful figure.
"Even the senior leadership of our intelligence service was not aware of this," he said, calling it a "rogue operation".
These remarks followed Saudi Arabia's admission on Friday that Mr Khashoggi had died. A statement from the public prosecutor said he had been killed when a "fist fight" broke out with some of the people he was meeting inside the consulate.
Until this point – for 18 days – the authorities had maintained that the Saudi critic was last seen leaving the building alive.
They then said they had arrested 18 people, sacked two aides of Mohammed bin Salman and set up a body, under his leadership, to reform the intelligence agency over the killing.
Both King Salman and the crown prince called Mr Khashoggi's son, Salah, on Sunday to express their condolences over his death, the Saudi Press Agency reports.
Salah Khashoggi resides in Saudi Arabia and, according to the Wall Street Journal, had been barred from leaving the country to visit his father who was living in self-imposed exile in the US.
Meanwhile, Mr Khashoggi's fiancée. Hatice Cengiz, who raised the alarm about his disappearance after waiting for him for hours outside the consulate, was given 24-hour police protection, Turkish state news agency Anadolu reports.