Iraq's prime minister said that captive Islamic State militants told his intelligence agents of an alleged plot to attack subways in the United States and Paris.

There was no immediate comment from Washington or France. A half-dozen French officials contacted by The Associated Press said they knew of no plot.

Prime Minister Haidar al-Abadi said he was told of the purported plot by officials in Baghdad, and that it was the work of foreign fighters who had joined the Islamic State group in Iraqi, including French and US nationals.

Asked if the attacks were imminent, he said, "I'm not sure." Asked if the attacks had been thwarted, he said, "No, it has not been disrupted yet... this is a network."

"Today, while I'm here I'm receiving accurate reports from Baghdad that there were arrests of a few elements and there were networks from inside Iraq to have attacks ... on metros of Paris and U.S.," al-Abadi said, speaking in English. "They are not Iraqis. Some of them are French, some of them are Americans. But they are in Iraq."

He made the remarks at a meeting with journalists on the sidelines of a gathering of world leaders at the United Nations General Assembly.