ISTANBUL — Friends and supporters of the Saudi dissident journalist Jamal Khashoggi held funeral prayers over an empty marble slab at one of Istanbul’s holiest mosques on Friday, declaring him a martyr and vowing to unmask those behind his murder in the Saudi Consulate 45 days ago.
Arab dissidents, journalists and activists filled the outer courtyard of the Fatih Mosque on Istanbul’s historical peninsula in a farewell to Mr. Khashoggi that was as political as it was religious.
“This is a responsibility, a debt, a duty in our religion that lies with the ones who remain alive, and we gathered to fulfill this religious duty,” said Yasin Aktay, a close friend of Mr. Khashoggi’s, and a senior member of the ruling Justice and Development Party in Turkey.
Mr. Khashoggi was murdered Oct. 2 in the Saudi Consulate, where he had gone to obtain papers that would allow him to marry. His remains have not been found.
“Praying for the funeral while there is no body is unusual,” Mr. Aktay added. “This is a situation that should be a slap to the face of those who committed this shame.”
Groups were also gathering in Mr. Khashoggi’s memory around Turkey, in the Saudi Arabian cities of Mecca and Medina, and in Washington and London, he said.
Yet even as the government showed support for Arab dissidents gathered in Istanbul to honor Mr. Khashoggi, the police made a new round of arrests in a crackdown that has led to the detention of over 100,000 people and the suppression of dissent in Turkey.
Two prominent university professors were among at least 12 people detained early Friday and charged with trying to overthrow the government for their participation in the Taksim Square democracy protests in 2013.
At Mr. Khashoggi’s funeral prayers, Mr. Aktay and other speakers rejected the latest official announcement from the Saudi chief prosecutor. On Thursday, the prosecutor said that the killing of Mr. Khashoggi was an improvised decision by a team of agents who had traveled to Istanbul, and that the de facto ruler of Saudi Arabia, Crown Prince Mohammed bin Salman, was not responsible.
Turkish officials have said that such a team, which included security officials close to the crown prince and a forensic specialist equipped with a bone saw, arrived with a premeditated plan to execute Mr. Khashoggi and dismember and dispose of his body. They say such an operation could have been ordered only from the highest level.
President Recep Tayyip Erdogan of Turkey has said he is confident that King Salman of Saudi Arabia had no part in the murder, but he has asked questions about the crown prince’s role.
Turkish officials have described the Saudi investigation so far as insufficient.
At the funeral, several speakers repeated this point.
“We do not believe that story that we are asked to believe,” said Mr. Aktay, who is an adviser to Mr. Erdogan. “We are asking what were his killers after. We will continue to ask. We ask who are the real killers, the instigators, and we will continue to ask.”
The Egyptian politician and former presidential candidate Ayman Nour, a longtime friend of Mr. Khashoggi’s, said the Saudi prosecutor’s findings did not “provide us with the justice we have been waiting for.”
He added, “This is not a legal or a political statement, but an attempt to get away from criminal and political accountability.”
Under Mr. Erdogan, Turkey has become a home for many Arab dissidents and refugees from the Arab Spring uprisings and counterrevolutions, prominent among them members of the Egyptian Muslim Brotherhood, and Syrian and Yemeni politicians and activists.
Arab dissidents have led the calls for justice for Mr. Khashoggi, declaring him the latest victim of Arab states intent on suppressing the popular uprisings.
“Jamal expected and was very hopeful that change would come from all these revolutions,” Mr. Nour said last week at an international conference on Yemen in Istanbul. “I believe the second wave will come after the death of Jamal Khashoggi. Starting in this room and with the people who are here.”
Also speaking at the funeral was Turan Kislakci, a friend of Mr. Khashoggi’s and the director of the Turk Arab Media Association.
“Jamal’s last words were ‘I am suffocating,’” he said, referring to audio recordings reported in the Turkish media of the moment of Mr. Khashoggi’s death.
“It is not only Jamal who was suffocated, all of humanity is,” he continued. “All the Islamic world is suffocating. They are being suffocated in Palestine, in Syria, in Libya, Yemen. Let this be the last suffocation. Let the world not suffocate again, let it breathe.”
In Istanbul, among those detained in early-morning raids were Turgut Tarhanli, the dean of the law faculty at Bilgi University, and Betul Tanbay, a well-known mathematician at Istanbul’s foremost institution, Bogazici University.
Also detained were the producer and author Cigdem Mater, the academic Hakan Altinay and other staff members of the Anadolu Kultur Association, a cultural foundation set up by the philanthropist Osman Kavala who has been imprisoned without trial for over a year.
A police report said the detained were accused of organizing protests, bringing in trainers and professional activists, and forming new media outlets to spread protests around Turkey.
The arrests drew sharp criticism from the European Court of Human Rights and business and human rights groups.
“It is sad to start the day with reports of detention of many academics,” Erol Bilecik, the head of a Turkish business association, posted on his Twitter page.
Turkey’s Human Rights Association said Mr. Tarhanli, the law dean, was a “prominent human rights defender who has long been engaged in the struggle for rule of law and educated many a legal expert, and other individuals.”