A teenager armed with a handgun and shotgun killed a fellow student and wounded five other people at a high school in the midwestern US state of Iowa on Thursday, authorities said.

The shooting at around 7:30 a.m. triggered a major police response with emergency vehicles and armed units rushing to Perry High School, where classes had not yet started for the day.

The victim who died was in sixth grade, meaning aged 11 or 12, and was likely in the high school for a breakfast program, Mitch Mortvedt, assistant director of the Iowa Division of Criminal Investigation, said.

Among those injured by the 17-year-old shooter were four other students and a school administrator, he added.

Responding authorities also found an improvised explosive device in the school, which they disabled.

"Officers immediately attempted to locate the source of the threat and quickly found what appeared to be the shooter with a self-inflicted gunshot wound," Mortvedt told reporters, without confirming media reports that the shooter was dead.

High school student Ava Augustus told a local TV station that she hid in a classroom during the shooting. She ran out after authorities told her the incident was over, and recalled seeing "glass everywhere, blood on the floor."

"I get to my car and they're taking a girl out of the auditorium who had been shot in her leg," she told the local NBC affiliate.

The injuries sustained by the five wounded victims were not life-threatening, Mortvedt said.

CNN reported that Thursday was scheduled to be the first day of classes for the new semester, according to the school district's calendar.

The school announced that classes Friday would be canceled and that counseling would be available for students.

According to a database maintained by news outlet Education Week, the Perry incident is the second school shooting so far this year, adding to the 182 recorded since 2018.

The first was the shooting outside a high school in Virginia reported a day earlier and involved a 15-year-old who allegedly shot a man. It was unclear if either were students.