Captured foreign Islamic State militants must be taken back by their home countries, the Kurdish-led forces in north-eastern Syria have said.

The Syrian Democratic Forces (SDF) said it would not put them on trial themselves and lacked the resources to hold them indefinitely.

The SDF, which controls the region, say they hold about 500 jihadists, and hundreds of their wives and children.

The captured IS fighters are reported to be from dozens of countries.

States that the IS jihadists came from have proven to be reluctant to take these dangerous men back, the BBC's Middle East analyst, Alan Johnston, says.

IS militants seized large areas in Syria and Iraq in 2014 - but have seen been driven out from most the captured territory.

The SDF is being backed by the US-led coalition.

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On Thursday, Kurdish foreign affairs official Abdel Karim Omar said that "around 520 Daesh [IS] mercenaries, as well as 550 women and around 1,200 children from 44 countries" were in the SDF's custody.

"It's a heavy burden that we can't carry alone.

"We will not try any IS fighter... We are trying as much as possible... to pressure governments to carry out their duties and take their citizens back."