Hours after the Turkish president accused Saudi Arabia of carefully plotting the "savage murder" of journalist Jamal Khashoggi, U.S. President Donald Trump weighed in to say that while he is still waiting for a full report, he thinks the Saudis engaged in "the worst coverup ever."

Saudi officials killed Khashoggi in their Istanbul consulate after plotting his death for days, Turkey's president Recep Tayyip Erdogan said Tuesday, contradicting Saudia Arabia's explanation that the journalist was accidentally killed.

He demanded the kingdom reveal the identities of all involved, regardless of rank.

Erdogan also said he wants Saudi Arabia to allow 18 suspects that it detained for the Saudi's killing to be tried in Turkish courts, setting up further complications with the Saudi government, which has said it is conducting its own investigation and will punish those involved.

Saudi Arabia has described the suspects as rogue operators, even though officials linked to 33-year-old Saudi Arabia's Crown Prince Mohammed bin Salman have been implicated in the killing.

Speaking later Tuesday, Trump said that Erdogan was "pretty rough" on Saudi Arabia in his remarks — but he also called Riyadh's handling of the events after Khashoggi's death "the worst coverup ever."

"Bad deal, should have never been thought of. Somebody really messed up," he told reporters in the Oval Office who asked about Khashoggi's killing. "Whoever thought of that idea, I think, is in big trouble.

"And they should be in big trouble," Trump said. But he also praised Saudi Arabia's longstanding record as an investor into the U.S., and as an ally. When asked about possible reprisals Saudi Arabia could face, he said Congress would play a major role.

Saudi Crown Prince Mohammed bin Salman meets with Khashoggi's son in Riyadh on Tuesday. (Bandar Algaloud/Saudi Royal Court via Reuters)

"In terms of what we ultimately do, I'm going to leave it very much — in conjunction with me — up to Congress," he said, noting that both Republicans and Democrats would have a say. He said he expects a report from his officials on what happened soon.

Secretary of State Mike Pompeo, meanwhile, said the U.S. will revoke visas for individuals identified as being responsible for the journalist's death.

The crown prince and his father, King Salman, received Khashoggi's ​son, Salah, and his brother, Sahel, at the Yamama Palace in Riyadh on Tuesday. A friend of the Khashoggi family told The Associated Press that Salah has been under a travel ban since last year. The individual spoke on condition of anonymity, fearing reprisal.

Turkey demands names

Riyadh had initially denied knowledge of the 59-year-old's fate before saying he was killed in a "fist fight" during "discussions" at the consulate. That version of events was greeted skeptically by several Western governments, straining relations with the world's biggest oil exporter.

"To blame such an incident on a handful of security and intelligence members would not satisfy us or the international community," Erdogan said in a speech to ruling party lawmakers in parliament.

"Saudi Arabia has taken an important step by admitting the killing. As of now, we expect of them to openly bring to light those responsible — from the highest ranked to the lowest — and to bring them to justice," the Turkish president said.

When the murder is so clear, why were so many inconsistent statements made? - Turkish President Recep Tayyip Erdogan

Erdogan's speech was previously pitched as revealing the "naked truth" about Khashoggi's slaying. Instead, it served to officially detail information already circulated by anonymous officials and the Turkish media in the days since the Washington Post columnist and U.S. permanent resident walked into the consulate on Oct. 2.

However, Erdogan kept pressure on the kingdom with his demands for Turkish prosecution of the suspects as well as punishment for the plot's masterminds.

"All evidence gathered shows that Jamal Khashoggi was the victim of a savage murder. To cover up such a savagery would hurt the human conscience."

UN Secretary-General Antonio Guterres stood by his earlier call for an independent and transparent investigation, said Farhan Haq, a deputy spokesman for the world body. Haq reiterated that Guterres can initiate a probe if key parties request it or if there is a legislative mandate from a UN body.

Crown prince implicated

Erdogan mentioned information that was earlier leaked by Turkish sources, including reports of 15 Saudi officials arriving in private jets shortly before Khashoggi's death as well as a man, apparently dressed in the writer's clothes, acting as a possible decoy by walking out of the consulate on the day of the disappearance.

"Why did these 15 people all with links to the event gather in Istanbul on the day of the murder? We are seeking answers. Who did these people get their orders from to go there? We are seeking answers," Erdogan said.

"When the murder is so clear, why were so many inconsistent statements made? Why is the body of a person who has officially been accepted as killed still not around?"

Turkish President Tayyip Erdogan says his government is determined that those found to be involved in the killing will 'not to escape justice.' (Tumay Berkin/Reuters)

Erdogan also demanded Saudi Arabia reveal the identity of a "local co-operator" who purportedly took Khashoggi's remains.

International skepticism has intensified since Saudi Arabia said on Saturday that Khashoggi, who had criticized the crown prince in his writing, died in a brawl. The case has shocked the world and raised suspicions that a Saudi hit squad killed Khashoggi after he entered the consulate, and then attempted to cover it up.

The G7 group of industrialized countries and the European Union issued a statement on Tuesday condemning Khashoggi's slaying in the "strongest possible terms" and demanding a credible investigation. The EU's top diplomat said the bloc is working with the G7 to co-ordinate a response.

Before Erdogan's announcement, top Turkish officials said Turkey would clarify exactly what happened to Khashoggi. A stream of leaks to national and international media has increased pressure on Saudi Arabia, which is hosting a glitzy investment conference this week that many dignitaries have decided to skip because of the scandal.

"As we all know, these are difficult days for us in the kingdom of Saudi Arabia," Energy Minister Khalid al-Falih told attendees seated in an ornate hall during the opening of the conference in Riyadh.

"Nobody in the kingdom can justify it or explain it. From the leadership on down, we're very upset of what has happened," al-Falih said

An image made from surveillance camera footage shows a man identified by Turkish officials as Maher Abdulaziz Mutreb walking toward the Saudi Consulate in Istanbul before Khashoggi disappeared on Oct. 2. The image was published Thursday by the pro-government Turkish newspaper Sabah. (Sabah via Associated Press)

Saudi Arabia said it arrested suspects and several top intelligence officials were fired over the killing, but critics alleged that the punishment was designed to absolve Prince Mohammed of any responsibility.

On Monday, leaked surveillance video showed a man strolling out of the diplomatic post hours after Khashoggi disappeared into the consulate, apparently wearing the columnist's clothes as part of a macabre deception to sow confusion over his fate.

The new video broadcast by CNN, as well as a pro-government Turkish newspaper's report that a member of Prince Mohammed's entourage made four calls to the royal's office from the consulate around the same time, put more pressure on the kingdom.

Turkish investigators, meanwhile, inspected a car belonging to the consulate and found three suitcases, a laptop computer and clothes inside, state television TRT reported. Authorities discovered the car at an underground garage in Istanbul on Monday.

A Saudi cabinet meeting, chaired Tuesday by the 82-year-old king, said Riyadh would hold to account those responsible for the killing and those who failed in their duties, whoever they were.

Saudi Arabia's foreign minister, meanwhile, said Tuesday that his country was committed to ensuring "that the investigation is thorough and complete and that the truth is revealed."

Foreign Minister Adel al-Jubeir, in Indonesia, also pledged that mechanisms will be put in place so that "something like this can never happen again."