A judge on Wednesday ordered Belgium to organise the return of six Belgian children and their mothers from a Syrian refugee camp overseen by Kurdish forces.

The children, all aged six or under, are the offspring of alleged jihadist fighters and Brussels has so far resisted calls for their repatriation.

Wednesday's ruling touches only on these six, but human rights defenders fear as many as 160 Belgian minors are trapped in the conflict zone.

A lower court had previously rejected a demand lodged by two women, each mother to three of the children, for their home government to intervene in the case.

But the Flemish-speaking Court of First Instance in Brussels has overturned that, ordering Belgium to take "all necessary and possible measures" to return them.

The state has been given 40 days to act or face fines of 5,000 euros per day per child.

And the court instructed Belgium to make contact with camp authorities, perhaps working through the diplomatic channels of a fellow European Union state.

Belgium must provide the children and their mothers with the appropriate identity papers to ensure a safe return.

As a proportion of its population, Belgium has been one of the main suppliers of Europeans travelling to fight for Islamist extremist groups in Syria and Iraq.