World Bulletin/News Desk

A former American soldier has joined Kurdish forces fighting against ISIL militants in northern Syria, a rare case of a lone U.S. citizen joining the fight against militants in Syria.

Jordan Matson of Wisconsin has joined the Kurdish People's Protection Units (YPG), who are mainly battling advances by ISIL militants close to Syria's borders with Turkey and Iraq, a spokesman for the Kurdish group said on Thursday.

YPG spokesman Redur Xelil confirmed Matson's presence with the group in an online note and said: "He is fighting in the Jazaa area." Jazaa is in northeast Syria and has seen heavy fighting between the YPG and fighters of ISIL.

Matson's mother, speaking through a friend at her home in Sturtevant, Wisconsin, declined to comment. The U.S. army said that a Jordan Matson of Sturtevant was a private first class in the U.S. Army from May 2006 to November 2007.

U.S. officials say about 100 Americans have gone to Syria to join groups fighting there against Syrian President Bashar al-Assad.

At a meeting last week chaired by U.S. President Barack Obama, the U.N. Security Council said all countries should make it a serious criminal offense for their citizens to fight abroad with militant groups.

The United States has no specific law preventing individuals from joining such groups, but it has anti-terrorism laws that it has used to prosecute those associated with such groups.

The YPG has not been designated by the United States as a terrorist organization but it has close ties to the Kurdistan Workers Party (PKK) in Turkey, which does have such a designation. The PKK has spent three decades fighting for autonomy for Turkey's Kurds.

"We have warned, as you know, U.S. citizens to defer all travel to Syria. We recommend any U.S. citizens remaining to depart immediately," State Department spokeswoman Jen Psaki said at her daily briefing.

"We also, of course, remain concerned about any citizen traveling to take part in military operations," said Psaki, who added she was aware of the reports about Matson having gone to Syria but declined to comment on his case for privacy reasons.

The Kurds in Syria and Iraq have become de facto allies of the United States, which is leading an international coalition to fight ISIL both in Syria and Iraq.

Xelil, who said he had met Matson, sent a link to online photos on a Kurdish news agency which he said were of the American. They show a smiling young man in an army shirt with a white and black scarf wrapped around his head. Xelil declined to give further details.

A Facebook page for Jordan Matson says he attended Case High School in Racine, Wisconsin and is 28. A friend of Matson's said he told online gaming friends about two months ago that he was joining a "private army" to fight ISIL.

"He told us in the community that he was getting hired by a private army and he let us know two to three months in advance," said Miguel Caron by telephone from Montreal.

"He sent me a personal Facebook message on the 16th of September saying 'hey boss, I'm heading to Syria.'" Caron added.

Caron said Matson had posted on Facebook this week that he was in Syria. The post was disseminated via Twitter, but is visible only to Matson's friends on his Facebook page.

"For all who didn't know I'm in Syria fighting for the YPG against ISIS. I am ok, won't be able to get on the net very often. I was hit by a mortar a few days ago during a 6 hour firefight but i am fine," Caron confirmed the post as saying.