A soldier manning a Russian nuclear forces site strode into a guardroom in the dead of night and shot dead four comrades before killing himself.
A defence ministry spokesman said the soldier opened fire with an assault rifle on the four at the fuel depot of the unit in Siberia before shooting himself. Other soldiers in the guardroom escaped by hiding in the loft, he said.
The ministry gave no reason for the incident, but said the commander of Russia's nuclear forces had flown to the unit near the city of Krasnoyarsk to head the investigation.
Random killings by despairing soldiers are common in the underfunded armed forces, where bullying is rife. But such incidents have been rare among troops in charge of Russia's vast nuclear arsenal