PARIS, Dec 28 (Reuters) - Three French-born children belonging to suspected Islamic State militants and who were being held by Iraqi authorities have been flown back to Paris, a foreign ministry official said on Thursday.

The International Committee of the Red Cross (ICRC) said it was the first such repatriation of French children from Iraq.

France, like other European nations, is wrestling with how to deal with suspected militants and their families seeking to return from combat zones in Iraq and Syria, as well as those in detention, after Islamic State surrendered huge swathes of territory under military pressure.

It has suffered a series of deadly militant attacks over the past three years and is grappling with the threat of homegrown militancy as well as the risks posed by Islamic State fighters slipping back across French borders.

"Their return was organised in coordination with the authorities in Iraq," a foreign ministry spokesman told Reuters.

French media reported that the family had left France for Iraq in 2015. The father was killed during the battle for Mosul and Iraqi forces later detained the mother and her four children in July, media said.

She and her youngest child remain in detention in Iraq, said Vincent Brengarth, the lawyer acting on her behalf. Her three older children, aged between three and eight years, were now in foster care after arriving back on Dec. 18.

Reuters revealed in September that Iraqi authorities were holding about 1,400 foreign wives and children of suspected Islamic State combatants at a single camp after government forces routed the jihadist group from Mosul, its last major urban redoubt in Iraq.

It was not clear if the three children had been among the same group.

French officials have indicated a preference for their citizens held in Iraq and found to be affiliated to Islamic State to be prosecuted there, although in mid-November President Emmanuel Macron said the fate of women and children should be examined on a case-by-case basis.

The head of France's domestic spy agency last month said some 700 men and women either of French nationality or who had resided in France, as well as 500 children, were in Iraq and Syria and linked to the militants. Several hundred others have already slipped back into France.

(Reporting by Charlotte Peytour and Simon Carraud; Editing by Richard Lough; editing by Ralph Boulton)