US-backed Syrian forces handed over to Iraq on Thursday 130 Iraqi members of the Islamic State group who were detained in Syria, an Iraqi military spokesperson said.
A spokesperson for the Kurdish-led Syrian Democratic Forces (SDF), however, denied the claim.
Iraqi security forces have received from the SDF "130 Iraqi Daesh fighters," General Yehya Rassoul, a spokesperson for Iraq's security media centre, told AFP using an Arabic acronym for ISIS.
"They used to fight in Iraq but when the battles were over they went to Syria where they were captured by SDF forces during recent fighting," he said.
Iraq declared victory over the jihadist group in late 2017 following a punishing campaign to dismantle its self-declared "caliphate" that once covered a third of the country.
Naim al-Kaood, the head of the security department in Iraq's Anbar province bordering Syria, told AFP the 130 ISIS fighters handed over were "wanted" by the Iraqi government.
A commander of the Hashed al-Shaabi paramilitary force, who declined to be named, said the jihadists were all Iraqi nationals and were transferred to authorities including members of military intelligence.
"Other groups will be handed over to Iraq, including families of the jihadists," said the commander.
The Syrian Observatory for Human Rights, a Britain-based war monitor, said that around 150 ISIS jihadists and family members were handed back to Iraq.
It said the relatives were taken from Syria to Iraq in trucks of the US-led coalition that has been fighting the jihadists in the two countries.
SDF spokesperson Mustefa Bali dismissed Iraq's claims.
"We deny this information part and parcel," he said.
SDF forces, backed by coalition air strikes, have trapped ISIS jihadists in less than half a square kilometre (a fifth of a square mile) in the village of Baghouz, their last sliver of territory in eastern Syria.
On Wednesday, hundreds of people, including women and children, were trucked out of Baghouz, but the SDF said that a large number of civilians remained inside.
At the height of its rule, ISIS imposed its brutal interpretation of Islamic law on a "caliphate" straddling Syria and Iraq that was roughly the size of the United Kingdom.
But the jihadists have since lost almost all their territory and hundreds of foreigners suspected of being ISIS fighters, as well as related women and children, are being held by the SDF.
Syria's Kurds have long urged their home countries to take the detainees back, but nations have been reluctant.