The UK, France and Germany have denounced writer Jamal Khashoggi's killing, demanding urgent clarification from Saudi Arabia over his death.
A joint statement said the explanation that Mr Khashoggi died after a "fist fight" in the consulate in Istanbul needed "to be backed by facts to be considered credible".
President Donald Trump earlier said he was "not satisfied" with the account.
And Turkey's president on Sunday vowed to reveal the truth about the death.
Recep Tayyip Erdogan said he would make a statement on the matter in parliament on Tuesday.
"We are looking for justice here and this will be revealed in all its naked truth," he told a rally in Istanbul.
Mr Khashoggi entered the consulate on 2 October to sort out divorce papers. Saudi Arabia initially said he had left shortly afterwards but has now admitted he died inside the building.
What is in the joint statement?
The UK, France and Germany expressed shock at the death, saying: "Nothing can justify this killing and we condemn it in the strongest possible terms."
They said they noted the Saudi explanation, but added: "There remains an urgent need for clarification of exactly what happened... beyond the hypotheses that have been raised so far in the Saudi investigation, which need to be backed by facts to be considered credible."
The nations said they would not make a judgement until further explanation had been detailed.
They said: "We therefore ask for the investigation to be carried out thoroughly until responsibilities are clearly established and that there is proper accountability and due process for any crimes committed."
What have other nations and groups said?
On Saturday, Mr Trump said: "I'm not satisfied until we find the answer."
But the US president said that, although sanctions were a possibility, halting an arms deal would "hurt us more than it would hurt them".
US Treasury Secretary Steven Mnuchin repeated that on Sunday, saying talk of sanctions was "premature".
Canadian Foreign Minister Chrystia Freeland said the Saudi "explanations offered to date lack consistency and credibility" while Australian PM Scott Morrison said: "This cannot stand. This will not do."
Amnesty International has called the Saudi explanation a whitewash of "an appalling assassination".
The Washington Post, which published articles by Mr Khashoggi, said the Saudi government had "shamefully and repeatedly offered one lie after another".
What's the latest from the Saudis?
Saudi Arabia's Foreign Minister Adel al-Jubeir spoke to Fox News on Sunday.
He suggested individuals had attempted to cover up the killing to his government and that it did not know the details.
"The individuals who did this did this outside the scope of their authority. There obviously was a tremendous mistake made, and what compounded the mistake was the attempt to try to cover up," Mr Jubeir said.
He added: "We want to make sure that those who are responsible are punished."
Mr Jubeir also said: "We don't know where the body is."
So far Saudi Arabia says it has arrested 18 people, sacked two aides of Crown Prince Mohammed bin Salman and set up a body, under his leadership, to reform the intelligence agency.
Do the Saudis have support?
Yes, from a number of regional neighbours.
On Sunday, Kuwait was the latest ally to praise King Salman for his handling of the case, saying it showed "the kingdom's keenness and commitment to establish the truth and its respect for legal principles to bring to account those behind this regretful event".
Egypt, Bahrain and the United Arab Emirates have been among those reflecting similar praise.
Saudi media on Sunday echoed this. The al-Riyadh newspaper reported a "wide welcome" of the government's "justice and firmness".
Where is the investigation now?
Turkey on Saturday said it would release all the details and that it would not allow a cover up.
Mr Erdogan's planned statement will be eagerly anticipated.
Although Turkey has so far stopped short of officially blaming Saudi Arabia for the killing, investigators have said they have audio and video evidence which shows Mr Khashoggi, was killed by a team of Saudi agents inside the consulate.
Police have searched the nearby Belgrad forest in Istanbul where they believe the body may have been taken and one official was hopeful its fate would be known "before long".
Both the consulate and the residence of the Saudi consul have been searched too.
Reuters reported on Sunday it had spoken to a Saudi official who said Mr Khashoggi had died in a chokehold after resisting attempts to return him to Saudi Arabia. His body was then rolled in a rug and given to a local "co-operator" to dispose of.
A Saudi operative then reportedly donned Mr Khashoggi's clothes and left the consulate.
The official said Saudi statements had changed because of "false information reported internally at the time".