A spokesman at the Saudi Defense Ministry, speaking on condition of anonymity, said the incident took place at around 11:15 a.m. local time (0815 GMT) on Tuesday when a grenade detonated during a training exercise at King Abdulaziz Military Academy in Riyadh, the Arabic-language newspaper Al-Riyadh reported.
He added that the blast killed one cadet and injured left nine people, including an instructor. The injured were taken to a military hospital, where one is in critical condition.
The official noted that an inquiry into the accident had begun.
The King Abdulaziz Military Academy is the oldest military academy in Saudi Arabia. It is the first choice for cadets from ground forces and police. The facility has students from other Persian Gulf and Arab countries as well.