Samples taken from the drains at the Saudi consulate in Istanbul showed traces of acid, it said, without quoting sources.
Saudi chief prosecutor Mojeb Al Saud travelled to Turkey in late October to discuss the investigation but Mr Erdogan later accused Saudi authorities of refusing to answer questions about the killing, such as who ordered it, the whereabouts of Khashoggi's body, and the identity of a "local collaborator" alleged to have helped dispose of it.
Saudi officials said initially that Khashoggi had left the consulate, later saying he died in an unplanned "rogue operation".
The foreign ministry said Hunt would meet Saudi Arabia's King Salman, Prince Mohammed, Abu Dhabi Crown Prince Sheikh Mohammed bin Zayed Al Nahyan, Saudi Foreign Minister Adel al-Jubeir, Yemeni Vice President Ali Mohsen and Foreign Minister Khaled Al Yamani. And on Monday, a Turkish official said Saudi Arabia sent two experts to Istanbul with the specific aim of covering up evidence after the murder.
"They (Saudi officials) also listened to the conversations and they know".
The businessmen said they would need to consult their attorney, who rejected the plan, and they told the Saudis they would not take part in assassinations.
Media reports have suggested that his body could have been chemically dissolved. Saudi Arabia's acknowledgment that the journalist had been killed in a fight inside the consulate came after two weeks of denials and growing pressure from Western allies to provide explanations.More news: Meg Ryan engaged to singer John Mellencamp
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UK Foreign Secretary Jeremy Hunt has said Khashoggi's murder had "possibly" given the U.S. and the UK a chance to put new pressure on Saudi Arabia over other issues.
The officials made the inquiry when Crown Prince Mohammed bin Salman ordered his advisers to ramp up military and intelligence operations overseas, The New York Times reported, citing three people familiar with the talks. Khashoggi was said to be dismembered and his remains have yet to be found.
US President Donald Trump and French President Emmanuel Macron both want to get "greater detail" about the events surrounding Khashoggi's killing, a French presidential spokesman said following a meeting between the pair Saturday in Paris.
Turkey is seeking the extradition of 18 suspects who have been detained in Saudi Arabia, so they can be put on trial in Turkey.
US officials said on Friday that the Trump administration is ending air refueling flights for the Saudi military campaign in Yemen and preparing sanctions against Saudis linked to the killing.
Erdogan repeated a demand for information on the whereabouts of Khashoggi's body.