ISTANBUL — Turkey said Monday that it has deported an American citizen and a Danish national suspected of belonging to the Islamic State militant group, as the government of President Recep Tayyip Erdogan began following through on a pledge to repatriate foreign-born extremists detained in Turkey.

An Interior Ministry spokesman, Ismail Catakli, did not identify the American or say where the person had been sent. Irish, German and French nationals detained by Turkey will be deported in the coming days, he added.

Thousands of foreigners flocked to the Islamic State as it began seizing territory in Iraq and Syria five years ago. The fate of many foreign militants who were detained after the Islamic State was driven from its last stronghold this year remains unresolved because many European states, citing the threat of attacks at home, have refused to repatriate them.

European states have insisted that the suspected Islamic State members face trial where they were captured or have sought to transfer them to Iraq for prosecution there. Some countries, including Britain, have stripped suspected militants of their citizenship to ensure they do not return home.

Last week, Turkey’s interior minister said the foreign detainees would be sent back to their countries, even in cases in which they had lost their citizenship and were effectively stateless. “We are not a hotel for anyone’s Daesh members,” Suleyman Soylu told reporters, using an Arabic acronym for the Islamic State, which is also known as ISIS. “What am I supposed to do with your terrorist?”

A State Department spokeswoman said Monday that the United States was “aware of reports of the detainment of a U.S. citizen by Turkish authorities. Due to privacy considerations, we have no further comment.” Turkish media reported that a U.S. citizen had been deported to Greece and that Greek authorities had refused to receive him.

A spokesman for Germany’s Foreign Ministry said Turkish authorities had notified Germany “about a total of 10 German citizens who are about to be deported in the course of this week.” German Interior Minister Horst Seehofer said citizens could “rest assured” that each case would be “carefully examined” by German authorities.

“We will do everything possible to prevent returnees with connections to IS from becoming a danger in Germany,” he said in a statement.

The problem of what to do with foreign-born Islamic State members gained new urgency after Turkey launched a military offensive in northern Syria last month, targeting a Kurdish-led militia alliance holding thousands of suspected Islamic State militants. Ankara views the Kurdish fighters in Syria as terrorists because of their links to the Kurdistan Workers’ Party, or PKK, which has waged a decades-long insurgency in Turkey.

The alliance, known as the Syrian Democratic Forces, holds about 10,000 suspected Islamic State members in Syria in about two dozen facilities — including about 2,000 fighters from around 60 countries, not including Syria and Iraq, according to Col. Myles B. Caggins III, a U.S. military spokesman.

Ankara’s offensive immediately raised fears that security at those facilities would be compromised. More than 100 people with alleged links to the Islamic State escaped from prisons and detention camps after the start of the Turkish operation, U.S. officials said.

Turkey has since faced growing international pressure to demonstrate that it is taking decisive action against the Islamic State. The pressure intensified last month when Abu Bakr al-Baghdadi, the group’s leader, was killed during a U.S. operation in Syria’s northern Idlib province — a few miles from the Turkish border, in a province ringed by Turkish military observation posts.

Over the past few weeks, Turkish authorities have announced the capture of hundreds of militants. More than 1,100 suspected Islamic State members are being detained in Turkey, Erdogan said last week, including members of Baghdadi’s family.

Turkish officials have begun insisting that Western states take back their nationals, forcing an overdue reckoning on the issue of the Islamic State detainees, according to human rights groups.

In a landmark ruling on Monday, a Dutch court decided that the Netherlands government had an obligation to repatriate 56 Dutch children held in camps in Syria, according to Andre Seebregts, a lawyer who represents dozens of Dutch children and mothers held in the camps.

The court found that 23 mothers who had appealed to return to the Netherlands did not have a right to come home unless their return was deemed necessary for the repatriation of the children, Seebregts said. Kurdish forces guarding the camps had indicated that they would not send the children without their mothers, he added.

It was likely that the women would be arrested as soon as they arrived in the Netherlands, he said. “It seems it’s safer for the Netherlands for these women to come back in a controlled environment than under the radar,” Seebregts said, adding that there appeared to be no alternative but to try them at home because the legal system in Iraq was “not up to standard.”

Morris reported from Berlin. Luisa Beck in Berlin and Louisa Loveluck in Baghdad contributed to this report.

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