An explosion at the University of Idaho injured a number of people when the testing of an experimental rocket went wrong.

Four people were taken to a local medical centre after the rocket exploded, the university said.

The rocket was being tested in a car park of the university's Moscow campus in front of a crowd of onlookers on Thursday (13 April). The test firing was close to the campus' power generator.

One local resident told news outlet KREM2 News that he heard the explosion at his home five miles away.

A student told local news channel KHQ: "When I did arrive [at the campus] there were some students yelling for help.

"I saw four people on the ground and they did not look responsive."

Emergency services attended. It is not known if the power generator was involved in the explosion.

The four injured individuals, all believed to be students, were taken to the Gritman Medical Center. One was said to be in a critical condition although the university later tweeted:

The names of those injured, who were members of the Northwest Organisation of Rocket Engineers, have not yet been released.