The killing of journalist Jamal Khashoggi was planned days in advance, the Turkish president, Recep Tayyip Erdogan has said in an address to MPs from his ruling party.
He said Turkey had strong evidence Khashoggi was killed in a premeditated and "savage" murder at the Saudi consulate in Istanbul on 2 October.
He also called for the suspects to be tried in Istanbul.
He demanded Saudi Arabia provide answers about where Khashoggi's body was, and who ordered the operation.
The Saudi kingdom has provided conflicting accounts of what happened to the Washington Post contributor. After weeks of maintaining he was still alive, the authorities now say he was killed in a rogue operation.
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Tuesday's address by President Recep Tayyip Erdogan coincided with the start of an investment conference in Saudi Arabia that has been overshadowed by the Khashoggi case, with dozens of government and business leaders pulling out.
What did the Turkish president say?
President Erdogan confirmed that 18 people had been arrested in Saudi Arabia over the case. However, he has not released any details of the evidence gathered about the killing.
He made no mention of any audio or video recordings mentioned in media reports in the days following the journalist's disappearance.
President Erdogan said three teams of 15 Saudi nationals had arrived in Istanbul on separate flights in the days and hours leading up to the murder.
A day before the killing, he said, some members from the group travelled to Belgrad forest, near the consulate - an area which was last week searched by Turkish police looking for the body.
He also described how the team had removed the security cameras and surveillance footage from the consulate building prior to Khashoggi's arrival - who was visiting to obtain documents for his forthcoming marriage.
"My demand is that 18 people be tried in Istanbul," he told MPs from his ruling AK party, adding that "all those who played a role in the murder" would be punished.