Saudi Arabia admitted on Saturday that journalist Jamal Khashoggi died inside its Istanbul consulate.
The Saudi public prosecutor said in a statement the journalist got involved in a fight that led to his death.
"The investigations are still underway and 18 Saudi nationals have been arrested," said the statement.
Saudi TV said King Salman had ordered the dismissal of senior royal court advisor Saud al-Qahtani, believed to be close to Crown Prince Mohammed bin Salman and the deputy head of intelligence chief Ahmed Asiri.
This acknowledgement comes after two weeks of denials from the Saudi government that it had anything to do with his disappearance.
At a rally in Arizona, US President Donald Trump said he was content with the Saudi account of the journalist's death.
"I think it's a good first step, it's a big step. It's a lot of people, a lot of people involved, and I think it's a great first step," he said.
However, he was cautious not to mention any sanctions against his middle eastern ally.
A critic of the crown prince who lived in the United States and was a Washington Post columnist, Khashoggi went missing on October 2 after entering the Saudi consulate in Istanbul, Turkey, to obtain documents for his upcoming marriage.
Turkey officials said they believed the journalist was killed inside the consulate, a claim Saudi Arabia denied until now.
Khashoggi's body has not yet been found by Turkish authorities.
Other western powers have yet to react to Riyadh's explanation of the events.
His Turkish fiancee, Hatice Cengiz, tweeted in Arabic: "The heart grieves, the eye tears, and with your separation we are saddened, my dear Jamal."