Two Saudi National Guard soldiers have been killed in an accidential blast during a training mission east of Riyadh, state news agency SPA reported.
The accident, in which two other soldiers were hurt, took place Tuesday during "a regular training mission using live ammunition," said National Guard ministry spokesman Colonel Khaled al-Muqbel.
A "bomb exploded inside an army vehicle, burning it completely," Muqbel said, adding that an investigation had begun.
The National Guard is the kingdom's parallel army and a pillar of the ruling royals, recruited from tribes that have traditionally backed Saud dynasty rule.
It is a trained army of between 180,000 and 200,000 men, divided into infantry units, mechanised brigades, special units and military police.
It operates in parallel, and as a palace-directed counter balance, to the regular Saudi ground forces.
The National Guard's role is mainly to support the interior ministry in preserving security, combatting terrorism, and protecting vital installations.
It also assists the defence ministry, if needed.
In May, King Abdullah upgraded the unit to a ministry headed by his son Prince Mitab.
King Abdullah himself led the National Guard from 1962 until 2010, when he transferred command to Mitab.