Jeremy Hunt has challenged Saudi Arabia to explain what happened to journalist Jamal Khashoggi following his disappearance earlier this month.
The UK, France and Germany have demanded a “complete and detailed response” from Saudi Arabia over the disappearance of the Washington Post columnist.
Reports claim the writer was killed while visiting the Saudi consulate in Istanbul, with Turkish authorities reported to have obtained audio and video recordings of the alleged murder.
Speaking from his official country residence in Kent, Mr Hunt said: “None of us know what happened but we are all extremely concerned about the stories that have emerged and the country that can help us get to the bottom of this is Saudi Arabia. So what happens from now on is absolutely up to Saudi Arabia.
“What they need to do is co-operate fully with the investigations that the Turks are asking us to do and to get to the bottom of this.
“If, as they say, this terrible murder didn’t happen then where is Jamal Khashoggi? That is what the world wants to know.
“If they have got nothing to hide then they will, and should, co-operate.”
Mr Hunt and his French and German counterparts have issued a joint statement saying they had “grave concerns” about the situation and called for a credible investigation into what happened.
“Defending freedom of expression and a free press and ensuring the protection of journalists are key priorities for Germany, the United Kingdom and France,” the three ministers said.
“In this spirit, light must be shed on the disappearance of Saudi journalist Jamal Khashoggi, whose family has lost contact with him since October 2.”
Mr Hunt, France’s Jean-Yves Le Drian and Germany’s Heiko Maas said they were treating the incident with “the utmost seriousness”.
“There needs to be a credible investigation to establish the truth about what happened, and – if relevant – to identify those bearing responsibility for the disappearance of Jamal Khashoggi, and ensure that they are held to account,” they said.”
The disappearance of Mr Khashoggi has placed the relationship between the Gulf kingdom and the West under intense strain.
US President Donald Trump has threatened “severe punishment” if authorities determine Saudi Arabia was behind Mr Khashoggi’s disappearance.
The Saudi government has dismissed the allegations against it as “baseless”.
The intervention by Mr Hunt and his allies followed criticism from Labour about the Government’s response.
Shadow foreign secretary Emily Thornberry said there had been “nothing but pusillanimous mutterings” from Mr Hunt on the issue.
“They’re playing catch-up with Donald Trump when it comes to condemnation of this and actually taking action and being prepared to stand firm.”
Ms Thornberry said the alleged murder was “yet more evidence of how the Saudi prince in particular appears to be out of control” and “this country has had enough”.
Commons Foreign Affairs Committee chairman Tom Tugendhat said on Saturday the UK should work with its allies on its response, and International Trade Secretary Liam Fox should boycott the Future Investment Initiative in Riyadh later this month if Saudi involvement in Mr Khashoggi’s disappearance was proven.
The Department for International Trade said: “The Secretary of State’s diary is yet to be finalised for the week of October 22, we will update on his activity in due course.”
A critic of Saudi Arabia’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 on October 2 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.