An American fighting for the Islamic State group was taken into custody in northern Iraq after he left territory controlled by the militant group, according to two Kurdish officers, one of whom arrested him.

"This person's name is Mohammed Jamal Amin, he holds US citizenship, has a Palestinian father and an Iraqi mother," General Sitei, commander of the Peshmerga's 8th brigade, said.

Both officers said it appeared the man was intending to escape both the Islamic State group and Kurdish forces but handed himself in after Peshmerga fighters opened fire on him near the frontline in the village of Golat.

Captain Daham Khalaf said they had spotted the fighter hiding in long grass around dawn and waited until the sun rose before surrounding him: "He shouted 'I am a foreigner'," Captain Khalaf said, describing him as bearded and dressed in black.

The fighter did not have a passport but was carrying US$4,000 (AU$5,323) in cash in various currencies, an American driving licence and spoke English and broken Arabic, General Sitei said.

"He said the situation with ISIS is not good," General Sitei said, noting that the fighter appeared tired.

"We gave him food and treated him with respect and handed him over to military intelligence."

The fighter was unarmed but carrying three mobile phones and said his father was Palestinian and his mother from the Mosul area in Iraq, both officers said.

"He said: 'No-one take my photo', but we did," Captain Khalaf said.

The US State Department said it was aware of the reports that a US citizen said to have been fighting for the Islamic State group was captured by Kurdish Peshmerga forces in northern Iraq.

"We are in touch with Iraqi and Kurdish authorities to determine the veracity of these reports," a State Department official in Washington said on the customary condition of anonymity.

Reuters/AFP