TEHRAN, Young Journalists Club (YJC) -"Nothing can justify this killing and we condemn it in the strongest possible terms," the three countries said in a joint statement on Sunday.
"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 statement added.
The three European countries stressed the importance of making more effort, saying they expected to establish the truth and ensure proper accountability for any crimes committed.
Saudi Arabia on Saturday admitted that the critic had died in the consulate after "discussions" at Riyadh's mission in Istanbul turned into "a brawl and a fist fight." It followed Saudi Arabia's denial for two weeks of its role in Khashoggi's disappearance on October 2.
An hour later, another Saudi official attributed the death to a chokehold.
Khashoggi was a Washington Post columnist and lived in the US, having fled Saudi Arabia in September last year.
In a joint statement issued on Saturday, German Chancellor Angela Merkel and Foreign Minister Heiko Maas strongly denounced Khashoggi's killing, rejecting Riyadh’s “inadequate” explanation on the death of the prominent critic.
"We condemn this act in the strongest terms," the German statement said, adding, "We expect transparency from Saudi Arabia about the circumstances of his death ... The information available about events in the Istanbul consulate is inadequate."
French Foreign Minister Jean-Yves Le Drian also on Saturday condemned "this murder in the strongest terms" and said," The confirmation of Mr. Jamal Khashoggi's death is a first step toward the establishment of the truth. However, many questions remain unanswered."
British Brexit Minister Dominic Raab said on Sunday that Saudi Arabia's explanation of how the journalist was killed was not "credible."
Raab told the BBC that there was a "serious question mark over the account that has been given," adding, "We support the Turkish investigation into it and the British government wants to see people held to account for that death."
Erdogan vows to reveal 'naked truth' over Khashoggi death
Turkish President Recep Tayyip Erdogan said on Sunday that his country would reveal the "naked truth" over the dissident journalist's killing, saying he would make a full new statement on the case when he would address his ruling party MPs in parliament on Tuesday.
"We are looking for justice here and this will be revealed in all its naked truth, not through some ordinary steps but in all its naked truth," Erdogan told a rally in Istanbul.
Turkish officials have said they believe that 15 Saudi men who arrived in Istanbul on two flights on October 2 -- the day when Khashoggi entered the consulate -- were connected to his death.
Riyadh on Saturday announced the arrest of 18 Saudis and the sacking of two top aides of Crown Prince Mohammed bin Salman, as part of its "probe" into the killing.
"Why did those 15 men come here? Why were 18 people arrested?" the Turkish president asked.
The Turkish leader has so far refrained from making strong statements about Khashoggi's death of, often referring to a prosecutors' investigation into the killing.
‘Turkey will not allow cover-up in Khashoggi’s killing’
Also on Sunday, a senior member of Turkey’s ruling AK Party said the country will not allow a cover-up after the killing of Khashoggi at the Saudi consulate in Istanbul
"If the incident transpired as it has been told across the world, there is no way Saudi officials can cover this up by saying a team from Saudi Arabia came and two or three men among them murdered him," Reuters reported deputy chairman of the AKP, Numan Kurtulmus, as telling CNN Turk in an interview.
"A crime committed in a consulate cannot be carried out without the knowledge of the senior state officials of that country. If this crime was really carried out as has been said, if the evidence really leads to that conclusion, the situation will be dire and this must have very serious legal consequences," he added.
Sen. Corker: bin Salman responsible for Khashoggi’s death
A leading Republican U.S. senator said on Sunday he believed Saudi Crown Prince Mohammed bin Salman was responsible for the death of dissident journalist Jamal Khashoggi.
"Do I think he did it? Yes, I think he did it," Senator Bob Corker, chairman of the Senate Foreign Relations Committee, said in an interview with CNN's "State of the Union."
Corker said he was waiting for investigations to be completed and hoped that Turkey would share any audio tapes of the killing of Khashoggi in the Saudi consulate in Istanbul.
However, he made it clear he believed the Crown Prince Mohammed directed the murder, saying that if the crown prince had ordered the murder, "he's now crossed the line, and there has to be a punishment and a price to pay for that."
"Let's let this play out, but my guess is that at the end of the day the United States and the rest of the world will believe fully that he did it," the US senator noted.
Khashoggi killing ‘huge and grave mistake’: Jubeir
In a relevant development, Saudi Foreign Minister Adel al-Jubeir said the killing of Khashoggi inside the Saudi consulate in Istanbul was a "huge and grave mistake," promising punishment for those responsible for the incident.
Condoling with Khashoggi's family, Saudi Arabia's top diplomat said, "This is a terrible mistake. This is a terrible tragedy. Our condolences go out to them. We feel their pain."
Jubeir, who was speaking in an interview with Fox News, added, "Unfortunately, a huge and grave mistake was made and I assure them that those responsible will be held accountable for this."
Claiming that Saudis do not know how Khashoggi was killed or where body is, Jubeir said Saudi officials were trying to find out where Khashoggi's body was and determine what happened.
The Saudi foreign minister also alleged that the crown prince was not aware of the incident and has denied knowledge of it.
Source: Press TV