Heads have started rolling after Saudi Arabia finally admitted journalist Jamal Khashoggi was 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 doesn't want to cancel a multi-billion 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 canceling $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."

'Insulting'

Karen Greenberg, director of the Center on National Security, said she was "surprised" by the Saudis' story about Khashoggi's death.

"They knew they had to come up with a story, and this is what they think is the best story for their purposes. It's at the very least insufficient, but it's also insulting. It's 'here's our story and we're sticking to it'."

Greenberg said Saudi King Salman could have reprimanded and removed his son from power for the killing.

"This is a brutal, horrifying, pointed assassination of a journalist who had strong ties to the West and was a resident of the United States. Each one of those is a line that you wouldn't have expected the king to allow to be crossed," Greenberg told Al Jazeera.

Saudi officials previously denied the writer had been killed inside the diplomatic facility, insisting Khashoggi had left the building before vanishing.

Turkish media reports have suggested Khashoggi was killed by a 15-person "assassination team" who flew in on two chartered planes to interrogate, torture and kill him.

A Saudi official familiar with the investigation told Reuters news agency the crown prince had no knowledge of the Khashoggi operation.

"There were no orders for them to kill him or even specifically kidnap him," said the source, speaking on condition of anonymity. "MBS had no knowledge of this specific operation and certainly did not order a kidnapping or murder of anybody."

'Unprecedented' admission

Over the past two weeks, Turkish intelligence had also disclosed a steady stream of leaks to the media, saying it had audio recordings that proved Khashoggi was killed inside the consulate building.

On Wednesday, the Turkish pro-government newspaper Yeni Safak, citing what it described as an audio recording of the journalist's killing, said the 15-member squad immediately accosted Khashoggi after he entered the consulate, cutting off his fingers and later decapitating him.

Aaron David Miller, Middle East analyst at the Wilson Center in Washington, to Al Jazeera the Saudi announcement was an effort to protect the powerful crown prince.

"Part of this is unprecedented. For an intel operation, for renditions and kidnappings, which they have done all the time, they have never disclosed or assumed any responsibility. And they've done it in response to pressure," said Miller.

"They are creating this cover story that his death occurred during a fist fight. It's another step in a big kabuki theater."

Turkish crime scene investigators this week searched the consulate building in Istanbul and the nearby residence of the Saudi consul general, and came out carrying bags and boxes. On Friday, investigators questioned staff and explored whether his remains could have been dumped outside Istanbul, Turkish media and a security official said.

Al Jazeera's Sinem Koseoglu, reporting from Turkey's capital, Ankara, said Turkish officials are accusing Saudi officials of attempting to thwart a joint Saudi-Turkish investigation, noting Mohammed bin Salman has been put in charge of leading the Saudi probe into Khashoggi's disappearance.

"It's a question of how to get away with murder," she said. "For the sake of the prosecution, the only thing missing is the body of Jamal Khashoggi in order to file an indictment . Now Turkey is going to ask, where is the body?"

'Unacceptable'

SPA also reported on Saturday that Saudi Arabia expressed its "deep regret" for Khashoggi's death and praised the Turkish government's cooperation.

"The kingdom expresses its deep regret at the painful developments that have taken place and stresses the commitment of the authorities in the kingdom to bring the facts to the public opinion, to hold all those involved accountable, and bring them to justice," it said.

The statement came shortly after US Secretary of State Mike Pompeo said Washington would consider a "wide range" of responses.

Al Jazeera's Andrew Simmons, reporting from Istanbul, said it remains to be seen how the US and Turkey respond to the revelation of Khashoggi's death.

"It's going to be extremely tense in the coming hours," he said. "Can they ride this out with this explanation? It remains to be seen," said Simmons.

"The pressure is now on the Turks to respond in some way to this assertion."

Intelligence agency restructuring

Meanwhile, SPA reported that Saudi King Salman had ordered the restructuring of the command of the general intelligence agency under the supervision of Mohammed bin Salman.

The order also included updating regulations, determining the agency's powers and evaluating its methods and procedures.

It said the king ordered the formation of a ministerial committee, headed by the crown prince, to oversee the restructure. It will include the interior minister, the foreign minister, the head of the intelligence agency and the chief of homeland security.

Observers questioned the viability of MBS overseeing the Saudi probe, considering he is a prime suspect in ordering Khashoggi's murder.

On Twitter, where Qahtani had launched vitriolic attacks against those he saw as the kingdom's enemies, he thanked the Saudi government for the "great opportunity they gave me to serve my country all those years".

"I will remain a loyal servant to my country for all times," he wrote on Saturday.

Assiri had no immediate comment.

•Adapted from a report by Al Jazeera and News Agencies.

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