Missing Saudi journalist being held at Istanbul consulate, says Turkey presidential spokesman

Two people close to Khashoggi, one of whom is his Turkish fiance, raised concerns about his whereabouts, saying he failed to emerge from the consulate.

The woman, who asked not to be named, said on Tuesday she had waited outside the consulate from 1pm local time (11am BST) and called the police when he had not reappeared.

"I don't know what's happening. I don't know if he's inside or if they took him somewhere else," she said by telephone from outside the compound.

Concerns were raised further after Saudi Arabia's official SPA news agency reported on Tuesday that an unnamed Saudi national was arrested and extradited to the kingdom by its Interpol agency.

Turkish and Saudi authorities, including the Istanbul consulate and the Saudi embassy in Washington, did not immediately respond to requests for comment.

Khashoggi fled Saudi Arabia in September last year after authorities banned him from writing in response to his criticism of the kingdom's rulers and US President Donald Trump.

Since then he has been in self-imposed exile in the United States, writing for The Washington Post.

"We have been unable to reach Jamal today and are very concerned about where he may be," the Post's international opinions editor Eli Lopez said in a statement.

"We are monitoring the situation closely, trying to gather more information. It would be unfair and outrageous if he has been detained for his work as a journalist and commentator."

The US State Department said it was investigating.

"We have seen these reports and are seeking more information at this time," an official said.