Turkish officials investigating the disappearance of Saudi journalist Jamal Khashoggi will search Saudi Arabia's consulate in Istanbul later on Monday, according to reports.
Turkish officials believe Mr Khashoggi was murdered in the consulate by Saudi agents nearly two weeks ago, but Riyadh strongly denies this.
Diplomatic pressure is growing on the Saudis to give a fuller explanation, reports BBC.
On Monday, Saudi Arabia's King Salman ordered an investigation into the case.
"The king has ordered the public prosecutor to open an internal investigation into the Khashoggi matter based on the information from the joint team in Istanbul," an official quoted by Reuters news agency said.
Last week, Turkey accepted a Saudi proposal to form a joint working group to investigate Mr Khashoggi's disappearance.
The latest moves come as more leading business figures say they will not attend a major investment conference in Riyadh later this month.
The head of JP Morgan, Jamie Dimon, is one of the latest high-profile executives to pull out.