Polat Can, a senior adviser to the Kurdish-led Syrian Democratic Forces (SDF), published details of the intelligence work that led to the US raid in which the founder of the Islamic State group was killed.

"Since 15 May, we have been working together with the CIA to track al-Baghdadi and monitor him closely," he said.

"Al-Baghdadi changed his places of residence very often," Polat Can said, adding that the asset managed to reach the house where the IS chief was believed to be hiding.

"Our own source, who had been able to reach al-Baghdadi, brought al-Baghdadi's underwear to conduct a DNA test and make sure (100%) that the person in question was al-Baghdadi himself," the adviser wrote on Twitter.

He said the US raid that killed Baghdadi in the northwestern province of Idlib was largely the result of SDF intelligence work, although Turkey's offensive against the Kurds launched October 9 had delayed the operation.

"Our intelligence source was involved in sending coordinates, directing the airdrop, participating in and making the operation a success until the last minute," Polat Can said.

US President Donald Trump, who announced the death of the world's most wanted man on Sunday, thanked Syrian Kurdish forces "for a certain support they were able to give us", but did not elaborate.

Trump said a DNA field test had confirmed his identity, and he also thanked Turkey, Iraq, Syria and Russia for their cooperation.

The Pentagon said Monday that Baghdadi's body had been disposed of at sea.