"On this occasion, and from this place where the spirit of Jamal has been lost, we clearly state that we will not accept compromises in the case of his murder", the group outside the consulate said in a statement, read out in Arabic, Turkish and English.
Before this, Jamal's son had allegedly been banned from leaving Saudi Arabia.
The son of murdered Saudi Arabian journalist Jamal Khashoggi, has arrived in the United States after leaving Riyadh with his family, an informed source told CNN on Thursday.
The Turkish government has so far declined to elaborate on the alleged audio recordings, but on Wednesday, the Washington Post reported that CIA Director Gina Haspel had listened to them.
The prince's olive branch to Turkey appeared to dial back an escalation in rhetoric on Tuesday, when Erdogan made a speech timed to coincide with the opening of the conference in which he said the killing of 59-year-old Khashoggi was premeditated and the culprits should be punished even if they were senior officials.
After first insisting Khashoggi left the consulate unharmed, Saudi authorities have given various accounts before on Thursday acknowledging that evidence from Turkey indicates the killing was premeditated.
The spy chief on Thursday briefed President Donald Trump on Turkey's findings and her discussions, White House spokeswoman Sarah Sanders said.
Also Thursday, the European Union issued a fresh condemnation of Khashoggi's killing and reiterated its skepticism that it could have been carried out without Mohammed's knowledge.
Turkish officials and some US lawmakers allege the crown prince ordered the operation in which Jamal Khashoggi killed.
Khashoggi, a Saudi insider-turned-critic who worked as a Washington Post columnist, was last seen on 2 October, when he entered the Saudi consulate in Istanbul to retrieve paperwork for his planned marriage.
French President Emmanuel Macron and British Prime Minister Theresa May both spoke via telephone with King Salman, according to a statement issued by the Saudi Foreign Ministry late Thursday, hours after the European Parliament's resolution passed.
"We will prove to the world that the two governments (Saudi and Turkish) are cooperating to punish any criminal, any culprit, and at the end justice will prevail", he said to applause.
An official at Turkey's presidential palace told Bloomberg, however, that while Turkey wants the crime to be uncovered, it had no interest in interfering in Saudi internal affairs or trying to influence who becomes the next king. They also photographed Saudi diplomatic vehicles scouting wooded areas in the days before Khashoggi disappeared.
Secretary of State Mike Pompeo said he is working with the Treasury Department on whether to impose sanctions on those found responsible for the journalist's death.