Turkish authorities were on Wednesday looking into claims the alleged mastermind of the failed July coup was involved in the assassination of Moscow's ambassador, but the Kremlin warned against jumping to conclusions.
Monday's murder of Andrei Karlov stunned Russia and prompted warnings of retribution from the Kremlin. But both sides responded by vowing to step up cooperation, particularly on the Syria conflict.
Off-duty Turkish policeman Mevlut Mert Altintas, 22, pumped nine bullets into Karlov at an art gallery in Ankara before he himself was killed by police in a shootout.
The pro-government press has repeatedly said that US-based Islamic preacher Fethullah Gulen, who Ankara blames for the attempted putsch, was behind the assassination plot.
And Turkish Foreign Minister Mevlut Cavusoglu told US counterpart John Kerry in a phone call on Tuesday that Ankara believed Gulen was involved.
"Turkey and Russia know that behind the attack... there is FETO," his ministry quoted Cavusoglu as saying, using Turkey's acronym for Gulen's organisation.
Gulen, who has lived in self-imposed exile in the United States since 1999, has strongly condemned the assassination.
Media reports said that books on Gulen's organisation were found at Altintas' home, while thorough checks are being made of his acquaintances at school and the police academy he attended.
Thirteen people, including close family members, have been detained over the killing and are being investigated for possible links to Gulen.
In a striking detail, the Hurriyet daily said Altintas, who served with the Ankara anti-riot police, had provided security for President Recep Tayyip Erdogan eight times since the July 15 attempt to overthrow the Turkish strongman.
Hurriyet writer Abdulkadir Selvi, known for his contacts in the ruling elite, said that on the day of coup bid Altintas had called in sick. But it was not clear what he did that night.
Turkey and Russia are jointly investigating the murder after an agreement between Erdogan and Russian President Vladimir Putin.
A team of 18 Russian investigators arrived in Ankara on Tuesday and spent the day at the crime scene after also witnessing the autopsy.
The Kremlin indicated it was not the time for hurried pronouncements on responsibility.
"In this case it is hardly worth hurrying to any conclusions until the investigation determines -- as our president said -- who was behind the murder of our ambassador," Kremlin spokesman Dmitry Peskov told reporters.
Commentators said that Putin would likely be unimpressed by any knee-jerk nailing of the crime on Gulen, who has become a byword for evil in Turkey after the coup bid.
"It can be assumed that the Russians will not be satisfied with explanations that 'Karlov's killer was a Gulenist'... They will instead ask for solid evidence," wrote Murat Yetkin, editor-in-chief of Hurriyet Daily News.
Since the coup, Turkey has piled pressure on the United States to extradite Gulen, a one-time Erdogan ally.
"We need to let them -- (the investigators) let the facts and the evidence take them where it is before we jump to conclusions," said State Department spokesman John Kirby.
Dramatic footage of Monday's assassination showed Karlov stumble and crash to the ground as Altintas brandished his automatic pistol at terrified onlookers who cowered behind cocktail tables.
The gunman shouted "Allahu Akbar" ("God is greatest") and "Don't forget Aleppo", vowing that those responsible for events in Syria would be held accountable.
Turkey and Russia stand on opposite sides of the Syria conflict, with Ankara backing rebels trying to topple Moscow ally President Bashar al-Assad.
But the rhetoric has warmed considerably since a reconciliation deal was signed earlier this year and Moscow and Ankara are now working closely together to evacuate citizens from the battered city of Aleppo.
Karlov's body was repatriated to Moscow on Tuesday after an emotional ceremony on the tarmac of Ankara's Esenboga airport attended by top Turkish officials.
In a highly unusual scene at an airport in mainly Muslim Turkey, a Russian Orthodox priest said prayers and swung incense over the coffin.
Karlov will be laid to rest on Thursday, Peskov said, adding that Putin had decided to postpone his major annual press conference scheduled for the same day to Friday in order to attend.