Five Turkish employees of the Saudi consulate have also given testimonies to prosecutors, Turkish media reported.
Mr Khashoggi, 59, went missing on that same day after entering the kingdom's office.
An adviser to Turkey's president on Monday rejected Riyadh's assertion that Jamal Khashoggi died in a fight, suggesting it "mocked" world opinion, as Western incredulity deepened over varying Saudi accounts of the journalist's killing.
In the days after Khashoggi vanished, Saudi officials initially said that he had left the consulate, implying premeditation on the part of the Saudi team.
Trump told the Post that "something will take place" in response to Khashoggi's death, but said the United States should not let the incident disrupt a possible $110 billion weapons sale to Riyadh he announced a year ago.
Following a telephone conversation between Saudi Arabia's King Salman and Donald Trump, the U.S. president told reporters that the king had denied all knowledge of Khashoggi's disappearance. "Why did it take 17 days to come up with this account?" asked Bruce Riedel, who served in the Central Intelligence Agency for 30 years and an expert on Saudi Arabia.
But the USA president said that, although sanctions were a possibility, halting an arms deal would "hurt us more than it would hurt them".
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Add Jamal Khashoggi as an interest to stay up to date on the latest Jamal Khashoggi news, video, and analysis from ABC News. South Carolina Senator Lindsey Graham said: "I find it impossible to believe that the Crown Prince was not involved".
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But even if the Saudis keep Trump on their side, they could face a reckoning from the U.S. Congress, where Republicans and Democrats alike have expressed outrage over the killing.
"The government is in agreement that we will not approve further arms exports for the moment because we want to know what happened", Altmaier told ZDF broadcaster.
The UK, France and Germany said on Sunday that Saudi Arabia's version of Khashoggi's death needs to be supported by "facts" to be considered "credible".
"They made the mistake when they killed Jamal Khashoggi in the consulate and they tried to cover up for it", he said.
Controversy over Khashoggi's death is particularly troublesome for Saudi Arabia as it gears up to host a high-profile investment summit in Riyadh.
She also questioned why they felt a need to defend MBS, saying, "What's so important about this prince?"
The top Saudi diplomat offered his condolences to Khashoggi's family, but disclosed no new information about how the writer was killed or where his body is.
According to the senior Saudi official, the Saudi team rolled up Khashoggi's body in a rug, took it out in a consular vehicle and handed it to a "local cooperator" for disposal.