The Turkish fiancee of slain journalist Jamal Khashoggi has called on US President Donald Trump and other leaders to ensure that his death in Istanbul is not covered up, while Saudi Arabia's top prosecutor on Tuesday visited the Saudi Consulate where officials from his government killed the writer.

Speaking at a memorial in London on Monday, Hatice Cengiz expressed disappointment in the “leadership of many countries.” Singling out Trump, she urged him to “help reveal the truth and ensure justice be served.”

“He should not pave the way for a cover-up of my fiance's murder. Let's not let money taint our conscience and compromise our values,” she said.

Cengiz also told the memorial that she wishes she had entered the consulate instead of Khashoggi.

She said in reference to an alleged Saudi hit squad sent to kill the columnist for The Washington Post: “If only I knew that would be the last time I would see my Jamal, his smile, hear his laughter, I would have stood in front of that murderous team myself.”

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Saudi Arabia's top prosecutor, Saud al-Mojeb, arrived at Istanbul's main courthouse on Tuesday for more talks with Istanbul's chief public prosecutor, Irfan Fidan, on the investigation into the killing, Turkey's state-run Anadolu Agency reported. The two had met for an hour and 15 minutes on Monday as part of an agreement between Riyadh and Ankara for cooperation over the investigation.

Al-Mojeb then went to the consulate and left after spending a little over an hour there.

Turkish President Recep Tayyip Erdogan said on Tuesday the investigation needs to be completed swiftly. “This needs to be solved now; there is no point in excuses,” Erdogan told journalists.

Erdogan said the prosecutor repeated to his Saudi counterpart Turkey's extradition request for 18 suspects detained in Saudi Arabia for the October 2 killing to be put on trial in Istanbul. Fidan asked al-Mojeb to reveal who sent this group, according to the president.

The country is also asking Saudi Arabia to help locate Khashoggi's body, which still has not been found. Erdogan said Riyadh must disclose the identity of an alleged local collaborator said to have been involved in disposing of Khashoggi's body.

Saudi Foreign Minister Adel al-Jubeir has said the kingdom will try the perpetrators and bring them to justice after the investigation is completed.

Under mounting international pressure, Saudi Arabia has changed its narrative about Khashoggi's killing several times, and has recently acknowledged that Turkish evidence shows it was premeditated.

Khashoggi had written critically of Saudi Arabia's crown prince in columns for The Washington Post.