Foreign Secretary Jeremy Hunt and his G7 counterparts have said they are "very troubled" by the disappearance of Saudi journalist Jamal Khashoggi and insist those responsible must be held to account.
It is suspected that the Washington Post columnist, who was critical of Saudi Crown Prince Mohammed bin Salman, was killed while visiting the Gulf kingdom's consulate in Istanbul.
Riyadh is a key ally for the West and US President Donald Trump compared what was happening to the accusations of sexual assault leveled against now-Supreme Court Justice Brett Kavanaugh during his confirmation hearing.
"Here we go again with you're guilty until proven innocent," Mr Trump said.
US secretary of state Mike Pompeo is in Turkey for talks following a meeting with the Saudi king and the crown prince on Tuesday.
In the statement, foreign ministers from the G7 group of leading economies, said: "We, the G7 Foreign Ministers, of Canada, France, Germany, Italy, Japan, the United Kingdom, the United States of America, and the High Representative of the European Union, affirm our commitment to defending freedom of expression and protection of a free press.
"We remain very troubled by the disappearance of prominent Saudi journalist Jamal Khashoggi. Those bearing responsibility for his disappearance must be held to account.
"We encourage Turkish-Saudi collaboration and look forward to the Kingdom of Saudi Arabia conducting a thorough, credible, transparent, and prompt investigation, as announced."
Mr Trump earlier tweeted that Saudi Arabia's crown prince had "totally denied" any knowledge behind the disappearance of Mr Khashoggi.
"Answers will be forthcoming shortly," Mr Trump said.
That attitude does not appear to be shared with Congress, as one prominent Republican senator said he believed that the crown prince, widely known as MBS, was involved.
"This guy has got to go," Senator Lindsey Graham told Fox. "Saudi Arabia, if you're listening, there are a lot of good people you can choose, but MBS has tainted your country and tainted himself."