"They aimed to ensure no sign of the body was left", said Aktay, who was a friend of the dissident Saudi writer.
The crown prince also reportedly urged President Trump's advisers Jared Kushner and John Bolton in the call to preserve the alliance between the US and Saudi Arabia.
One person familiar with the White House's deliberations said the administration expects to impose some sanctions on Saudi Arabia over the Khashoggi killing, in part because of bipartisan pressure from Congress.
The squad leader, Salah Muhammad al-Tubaigy, the head of forensic evidence in the Saudi general security department, started cutting Khashoggi's body while he was alive. He was last seen entering the consulate on October 2.
"The whole world has been shocked by this grotesque killing, and it's vital that we don't let the outrage fade away without justice being done", said Kate Allen, Amnesty International UK's director, in a statement.
We therefore respectfully call on you to immediately authorize an independent, worldwide investigation into the murder of Jamal Khashoggi that would lay the groundwork for identifying and holding accountable the perpetrators of this grievous crime.
"We know that the perpetrators are among the 18 suspects detained in Saudi Arabia", he wrote.
Hours before the memorial, Cengiz wrote about Khashoggi in an opinion piece for The Washington Post, saying, "As we witness the worldwide outrage at his killing, the perpetrators should know that they can never erase his vision for his beloved country".
Turkey's justice minister has meanwhile renewed a call for Saudi Arabia to cooperate in the investigation into the killing, saying "no one can escape responsibility".
Because of this, many countries have publicly cut military assistance to the Kingdom and have called for the government to clarify they account of what happened to Mr Khashoggi.
Saudi Arabia has faced backlash over the death, including from its allies, who have called for answers.
US President Donald Trump's response has kept shifting. However, he also said he was unwilling to sacrifice lucrative arms deals with the country.
"We're under no illusions about the challenges that are in Saudi Arabia and that remain", Rosenberg said. "We have to resolve our issues by our own will".
Earlier, the U.S. called for a swift cessation of hostilities in Yemen, where a Saudi-led coalition has been fighting rebels supported by its arch-enemy Iran.
"Today I am inviting the worldwide community to take serious and practical steps to reveal the truth and to prosecute those involved in a court of law".