A member of the Syrian Democratic Forces (SDF) walks on a street with his weapon in the northern Syrian town of Manbij on August 7, 2016. AFP/Getty Images

A US-led coalition air strike has killed 18 of its allied Syrian Democratic Forces (SDF) troops fighting against Isis in Syria, the US military has confirmed.

Coalition aircraft were given the wrong coordinates in a "misdirected" strike on April 11, US Central Command said on Thursday, resulting in a strike on an SDF position and the deaths of 18 partnered fighters in the north of the country.

The inaccurate coordinates reportedly came from the SDF itself.

The predominately Kurdish alliance of several fighting groups has managed to surround the Isis stronghold of Tabqa with both air and ground support from the US-led coalition.

It is not yet clear which air force of the several nations which lend air power to defeating Isis was behind the strike.

"The Coalition's deepest condolences go out to the members of the SDF and their families. The Coalition is in close contact with our SDF partners who have expressed a strong desire to remain focused on the fight against ISIS despite this tragic incident," a statement from Central Command said.

"The Coalition is assessing the cause of the incident and will implement appropriate safeguards to prevent similar incidents in the future."

The incident is the latest in several recent US-led strikes against Isis and al-Qaeda in Syria and Iraq which have accidentally hit allied or civilian targets.

In the Iraqi city of Mosul last month, a US strike killed up to 200 civilians in a single bombing.

BREAKING: Coalition says its own aircraft accidentally killed 18 SDF allies near Tabqah on April 11th [4th admitted 'friendly fire' event] pic.twitter.com/jxoELTEnhK — Airwars (@airwars) April 13, 2017

Independent News Service