The public prosecutor said a total of 18 people, all Saudi nationals, have been detained in connection to the probe.
Khashoggi, who contributed opinion pieces to The Washington Post, visited the consulate in Istanbul on October 2 to sort out marriage paperwork, but his fiancee saw nothing more of him after he entered.
Sen. Lindsey Graham (R-S.C.), who has called for strong sanctions against Saudi Arabia for its party in Khashoggi's death, expressed doubt about the official Saudi explanation. Some had social media posts self-identifying as being members of Mohammed's Royal Guard - raising questions about whether the crown prince had any knowledge of a plan to target Khashoggi. He said Khashoggi's death was caused by physical altercation inside the consulate.
If Khashoggi was fighting inside the consulate, he was "fighting for his life with people sent to capture or kill him", Schiff said, adding that if the Trump administration won't hold Saudi Arabia accountable for Khashoggi's death, Congress will.
Those fired included Crown Prince Mohammed bin Salman's adviser Saud al-Qahtani and deputy intelligence chief Maj. Since his disappearance, the kingdom had rejected Turkish fears he was killed and dismembered there as "baseless", but growing global pressure and comments by US officials up to President Donald Trump appears to have forced the kingdom to acknowledge the slaying.
It evolved into a major crisis for Prince Mohammed, a U.S. administration favourite whose image as a modernising Arab reformer has been gravely undermined.
'We have heard the same excuses time and again from Saudi Arabia on Yemen, and now on Khashoggi: when disgraceful atrocities are committed, they call them unintended mistakes, and the world does nothing, ' she said.
Trump said it's still "too early" to determine potential consequences but that he expects to know more by Monday.
The case has presented Trump with one of the most acute foreign policy crises of his almost two-year-old presidency. Beyond its statements attributed to anonymous officials, Saudi Arabia offered no evidence to support its claims.
The apparent circumstances of Khashoggi's disappearance caused worldwide revulsion. Turkish officials have said Khashoggi was killed and dismembered.
"The United States must not be complicit in this cover-up".
And Senate Foreign Relations Chairman Bob Corker of Tennessee noted that the Senate has demanded an investigation by the USA government.
He said the death of Mr Khashoggi was a "horrible event" that has not gone "unnoticed".
Turkish crime scene investigators this week searched the Saudi Consulate building in Istanbul and the nearby residence of the Saudi consul general, and came out carrying bags and boxes.