The military said three Russian bomber crew members died on Tuesday when their ejection seats were accidentally activated during initial inspections.
The Russian Defense Ministry said the accident took place at an air base in the Kaluga region, 145 km southwest of Moscow.
It said the crew of the Tu-22M3 long-range bomber was preparing for a training mission when the ejection system malfunctioned and accidentally shot the crew. The ministry said the altitude was not sufficient to open the parachutes and three of the four crew members succumbed to their wounds.
Russian media reported that among the victims was Colonel Vadim Beloslyudtsev, commander of the bombers unit stationed at the Shikovka air base near Kaluga.
Russian news reports said that a fourth crew member survived the accident and was taken to hospital.
An official investigation has been launched into the accident. Accidental activation of the rescue system is extremely rare, and some experts have speculated that it could be caused by electrical malfunction or human error.
The Tu-22M3 bomber is a long-range hypersonic, twin-engine bomber capable of carrying nuclear weapons.
It is estimated that about 60 of them are still in service with the Russian Air Force, and some have carried out aerial bombing missions to strike militants in Syria from their bases in Russia.
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