A rescue operation in the Russian Far East found the body of one pilot and rescued another after two fighter jets collided over the Sea of Japan during a training flight on Friday, Russian media reported.
Russian news agencies quoted the ministry as saying that the body of one pilot was found "without any sign of life."
The Russian Su-34 bombers touched in mid-air and fell into the sea near the Strait of Tartary, which separates Russia's Sakhalin island from the mainland, according to the country's Investigative Committee.
The committee also said it had opened a criminal investigation into the case.
The accident took place during a scheduled training exercise 35 kilometres (22 miles) from the shore in Russia's Far East, Russian news agencies reported citing the defence ministry.
According to Russian media, the pilots were able to eject from their jets.
Russia's television channel Zvezda, run by the defence ministry, earlier reported that one of the pilots was evacuated by air to the city of Khabarovsk.
It cited a ministry source as saying that the pilot's health was "satisfactory".
The number of missing pilots has not been confirmed. Russian media initially reported that two pilots had been rescued, but later cited authorities as saying that only one pilot had been found.
According to Zvezda, an ongoing rescue operation continued in severe weather conditions on Friday involving six ships, three helicopters and three planes.
Neither of the jets carried munitions.