The Kremlin has said that Turkey had provided Russian forces with the target location for air strikes in Syria that accidentally killed three Turkish soldiers.
Dmitry Peskov, the Kremlin spokesman, said on Friday that "there should not have been Turkish soldiers within the limits of these coordinates".
Besides the three fatalities, 11 soldiers were wounded in Thursday's incident, in which Russian forces, trying to target the Islamic State of Iraq and the Levant (ISIL) group, hit a building where the troops were deployed, according to the Turkish army.
Russia and Turkey have joined forces against ISIL, also known as ISIS, around Al Bab, where Turkish forces are battling the group on the ground.
Al Bab, 30km south of the Syria-Turkey border, is the last remaining significant ISIL stronghold in Syria's north.
"The situation is obvious, unfortunately. Our military, while launching strikes on terrorists, followed coordinates that were given to us by our Turkish partners," Peskov said.
Peskov stressed that the "causes of the incident are clear. There is no debate".
Asked if this was a mistake by the Turkish intelligence, he said the incident was caused by a communications failure.
The Turkish military said it considered the Russian incident an accident.
But it reiterated on Friday it had given the coordinates of the building to its Russian counterparts on Wednesday.
The Turkish statement said the soldiers had been in the same position for 10 days and that their coordinates had been communicated to Russia's Khmeimim airbase in Syria, and in person to the Russian military attache in Ankara.
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Russian President Vladimir Putin has expressed condolences in a telephone conversation with Turkish counterpart, Recep Tayyip Erdogan.
The Kremlin said that the two leaders agreed to "enhance military coordination in the course of the operation in Syria against the Islamic State fighters and other extremist organisations".
Speaking in the city of Afyon, Numan Kurtulmus, Turkish deputy prime minister, said it was important that Putin had expressed his condolences to Erdogan.
"From our side, the issue is being investigated. Initial information shows this was an accident ... and an undesired incident as a result of incorrect information, coordinates," he said.
However, Al Jazeera's Andrew Simmons, reporting from the Turkish border town of Gaziantep, said there appeared to be a dispute about what exactly happened.
"Now, Turkey is saying that they have been in their position with their army for 10 days and they had warned the Russians exactly where they were the day before they were struck," he said.
Against this backdrop, at least 23 ISIL fighters were "neutralised" in northern Syria by the Turkish military as part of the ongoing Operation Euphrates Shield, the Turkish army said on Friday in a statement carried by the Anadolu news agency.
In addition, Free Syrian Army (FSA), with support from Turkish troops, hit 154 ISIL targets, including shelters, headquarters, defence positions and vehicles, the statement said.
Turkish fighter jets also destroyed seven buildings used as hideouts, three headquarters and an arms depot of the group.
The Turkey-led Operation Euphrates Shield began in late August through FSA fighters backed by Turkish artillery and jets to improve security, support coalition forces and eliminate the threat along the Turkish border.
By contrast, Russia has been waging a bombing campaign in Syria in support of the forces of Syrian President Bashar al-Assad since 2015.
In yet another development on Friday, Syrian government forces and their allies in the Lebanese Shia Hezbollah group drew closer to Al Bab, according to the Syrian Observatory for Human Rights (SOHR).
According to the Britain-based SOHR, government forces made "an important and strategic advance by taking the village of Abu Taltal" in the southern sector of Al Bab.
"The regime forces are now 1.5km from Al Bab city," the SOHR said.
Source: Al Jazeera and news agencies