U.S. servicemen were seen by a Reuters correspondent near the frontline of an offensive launched on Sunday by Kurdish Peshmerga forces in northern Iraq that aims to retake a handful of villages from Islamic State east of their Mosul stronghold.

The U.S. servicemen were seen loading armored vehicles outside the village of Hassan Shami, a few miles east of the frontline.

U.S. Army Colonel Steve Warren, the spokesman for the U.S.-led coalition in Baghdad said: "U.S. and coalition forces are conducting advise and assist operations to help Kurdish Peshmerga forces."

Iraqi Kurdish Peshmerga forces in the early hours of Sunday launched an attack to capture a group of villages located about 20 km (13 miles) east of Mosul alongside the road to the Kurdish capital, Erbil.

Gunfire and airstrikes could be heard at a distance, while Apache helicopters flew overhead.

"The importance of liberating these villages is that it's a first step getting closer to Mosul," a Kurdish officer, Akram Mohammed, said in Hassan Shami.

"It's also to push ISIS threat away from the Kurdish area," he said, referring to one of the acronyms of Islamic State, the hardline Sunni militants who seized large amounts of territory in Syria and Iraq two years ago.