A student in the US has died after accidentally being struck on the head while volunteering at a hammer throwing contest.

First-year student Ethan Roser was hit by the hammer while working at a track and field competition at Wheaton College in Illinois.

Roser, from Cincinnati, Ohio, died on Saturday afternoon.

Witnesses say he collapsed as soon as he was struck by the object, described as a "16 pound ball attached to a steel wire".

A statement on the website of Wheaton College, where Roser transferred to in January, said: "We are deeply grieved, but, because of our faith in Christ, not without hope."

On Facebook, Roser's brother Johnathan Roser described his sibling as having lived a "powerful life".

"This afternoon, my youngest brother Ethan, who was just 19 years old, was called home to be with our Lord," he wrote.

"We are in shock and struggling to comprehend how we will live without him."