Saudi Arabia admitted journalist Jamal Khashoggiwas killed inside its consulate in the Turkish city of Istanbul, saying he died in brawl but made no mention of where his body is.
Preliminary results of investigations showed the dissident writer died after a fight broke out inside the building shortly after he entered, the official SPA press agency said on Saturday.
Saudi Attorney General Sheikh Saud al-Mojeb said Khashoggi died after "discussions" at the consulate devolved into an altercation.
"Discussions that took place between him and the persons who met him … at the Saudi consulate in Istanbul led to a brawl and a fist fight with the citizen, Jamal Khashoggi, which led to his death, may his soul rest in peace," the attorney general said in a statement.
"The investigations are still under way and 18 Saudi nationals have been arrested."
Royal court adviser Saud al-Qahtani and deputy intelligence chief Ahmed al-Asiri were fired from their positions, the statement said.
It remains unclear where Khashoggi's body is following his killing.
Khashoggi, a columnist for The Washington Post who wrote critically of Crown Prince Mohammed bin Salman's (MBS) rise to power, went missing on October 2 after entering the consulate in Istanbul to obtain documents needed for his upcoming marriage.
His whereabouts remained unknown since.
US President Donald Trump said he found Saudi Arabia's explanation about Khashoggi's credible.
"It's early, we haven't finished our review or investigation, but … I think it's a very important first step," he said.
Trump said sanctions against Saudi Arabia "could be" something he would consider but "it's too early to say" how the US will respond for now.
He said he does not want to cancel a multibillion-dollar arms deal with the Saudis in response to the admission of guilt.
"I would prefer, if there is going to be some form of sanction or what we may determine to do, if anything ... that we don't use as retribution cancelling $110bn worth of work, which means 600,000 jobs," he said.
Republican Senator Rand Paul tweeted: "We should also halt all military sales, aid and cooperation immediately. There must be a severe price for these actions by Saudi Arabia."