Singer Bad Bunny’s concert in Milan has been cut short after a severe hailstorm forced about 80,000 people to flee the outdoor concert venue.

Some concertgoers were struck on the head by hailstones “the size of walnuts” and injured on Saturday night (local time), Italian news agencies ANSA and Adnkronos reported.

Video images posted on social media show people ducking for cover, amid strong winds and heavy rain.

The storm began shortly after the Puerto Rican singer began his set at Milan’s Snai La Maura racecourse venue, which has a capacity of 80,000 people.

Local newspaper Mi Tomorrow said there was confusion in the crowd as the storm hit.

“In an initial announcement over the loudspeakers, organisers asked the audience to stay in their places and wait a few minutes, hoping the storm would pass quickly,” it wrote.

“As weather conditions worsened, a second message was issued ordering the evacuation of the area and directing attendees to the emergency exits.”

MilanToday said emergency services were brought in to help evacuate the racecourse.

“Firefighters evacuated the thousands of people who had gathered for the performance, the artist’s second show in the city,” it said.

“Several spectators were injured, particularly those hit on the head by the hailstones.”

The injured were treated by emergency medical services.

Event promoter Live Nation said later that the show would not be rescheduled and all ticket-holders would be reimbursed.

“Due to adverse weather conditions, including thunderstorms and hail, Bad Bunny’s concert scheduled for July 18 at the SNAI La Maura Hippodrome in Milan was interrupted, and the area was safely evacuated,” it wrote in an update on its website.

“Following careful assessment and every effort to reschedule the event, we regret to inform ticket holders that the concert has been cancelled and will not be rescheduled.”

Bad Bunny’s world tour is scheduled to wrap in Brussels on Wednesday.

-with AAP