Used underwear was among the evidence gathered by a defector to help pinpoint the location of Isis leader before he was killed by a US led strike, a senior Kurdish leader has claimed.

A defector embedded within Abu Bakr al-Baghdadi's camp also took blood samples from him, so he could be identified by DNA, General Mazloum Abdi told NBC News.

The informant, who was reportedly a close adviser to the terror group's leader, also provided Syrian Democratic Forces with a room-by-room description of Baghdadi's Syrian compound along the Turkish border, he added.

This information was then handed to US Special Operations forces, who were able to identify the Isis chief from the samples provided.

The informant collected the underwear three months ago and the blood sample was one-month old, Gen Mazloum said.

Donald Trump has however downplayed the role of Kurdish forces, who he was accused of abandoning when he withdrew US military personnel from northern Syria and leaving them at the mercy of Turkish forces who moved into the region.

The US president thanked Russia for allowing them to use the airspace in the region and Turkey.

But he only thanked Syrian Kurds for "certain information" and said that their involvement was "not a military role at all".

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"We had our own intel," Mr Trump said. "We got very little help. We didn't need very much help."

In an address to US police chiefs in Chicago, the president said he "destroyed the caliphate" with the death of al-Baghdadi.