"It is the first time a GSDF member has died during an overseas drill," the spokesman told AFP.
Maehara was delivering food supplies to members participating in the drill when the accident happened.
The exercise, codenamed Kamandag (meaning 'Venom'), marked the first time Japanese armoured military vehicles were used on foreign soil since the country adopted a pacifist constitution after its 1945 defeat.
But Japan is not involved in the combat component of the military exercises.
The 10-day exercise is being held at a Philippine navy base facing the South China Sea, some 250 kilometres (155 miles) from the Scarborough Shoal -- a territory claimed by Manila that was seized by China during a 2012 naval stand-off.
Local media reported that Maehara was in a vehicle driven by a Philippine man near the naval base.
A Philippine spokesman for the exercises declined to comment.
The US military stressed that Saturday's exercise was not aimed at China.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)