Media playback is unsupported on your device Media caption Ambassador to the UK Prince Mohammed bin Nawaf al Saud says he is "concerned about Jamal"

Saudi Arabia's UK ambassador has told the BBC he is "concerned" about missing Saudi journalist Jamal Khashoggi.

But Prince Mohammed bin Nawaf al Saud added it would be "premature" to comment on the issue at present.

Mr Khashoggi, a well-known critic of the Saudi government, has not been seen since visiting the country's consulate in Istanbul last week.

Meanwhile, Sir Richard Branson has said he has halted investing in Saudi Arabia over Mr Khashoggi's disappearance.

Mr Khashoggi's fiancée fears he has been kidnapped or killed while Turkish authorities in Istanbul believe he was murdered by Saudi agents.

Saudi Arabia denies killing Mr Khashoggi and insists that he left the consulate shortly after he arrived.

"There is an ongoing investigation and it would be premature of me to comment until we see the final results," Prince Mohammed said.

He added that Saudi Arabia "would like to know what happened" to Mr Khashoggi, and hoped the investigation would provide answers "soon".

Image copyright EPA Image caption Jamal Khashoggi has not been seen since entering the consulate in Istanbul

Foreign Secretary Jeremy Hunt and US President Donald Trump are among the political figures to have demanded answers from Saudi Arabia over the case, while Virgin boss Sir Richard has also added pressure on the Gulf kingdom.

The entrepreneur said he would be suspending his directorship of two tourism projects in the country, while Virgin would halt discussions with the Saudis over investment in its space projects.

Sir Richard said he "had high hopes for the current government" in Saudi Arabia - but was concerned by reports of state involvement in the disappearance of one of its own citizens.

"What has reportedly happened in Turkey around the disappearance of journalist Jamal Khashoggi, if proved true, would clearly change the ability of any of us in the West to do business with the Saudi government," he said.

Media playback is unsupported on your device Media caption CCTV footage shows missing journalist Mr Khashoggi entering the Saudi consulate in Istanbul.

A critic of the kingdom's de facto ruler Crown Prince Mohammed bin Salman, Mr Khashoggi was living in self-imposed exile in the US and writing opinion pieces for the Washington Post before he vanished.

He visited the consulate in Istanbul last Tuesday to obtain a document confirming he had divorced his ex-wife, in order to allow him to remarry.

Turkish officials have said he was killed on the premises and his body removed.

Saudi Arabia has described the allegation as baseless.