This explosion took place ten days after a series of blasts ripped through the same complex.
A Defence Ministry spokesman said eight people were killed and two injured while loading munitions for decommissioning.
Unlike the previous incident ten days ago, witnesses said the detonations were not heard in the centre of Ulyanovsk, a city of 635,000 people about 800km south east of Moscow.
The accident happened at Arsenal Number 31 in the central Russian city of Ulyanovsk, where an explosion earlier this month set of a number of munitions, lighting up the sky for several hours and forcing the evacuation of 3,000 people.
