Japanese fighter jets intercepted the Russian radar aircraft in international airspace over the Sea of Japan, according to the Japanese Self-Defense Force.
The Russian aircraft was believed to be an A-50 airborne early warning and control aircraft (AEW&C), the JSDF said in a statement.
The Russian A-50 command and control military aircraft is known in the West by the NATO codename Mainstay.
The A-50 is intended to detect and identify airborne and sea objects determining its position, bearing and speed. The objects data collected by the A-50 aircraft is transferred to command centers. In addition, this AWACS aircraft is able to direct aircraft to engage airborne and surface targets.
The A-50 can fly four hours at 1,000 kilometres (620 mi) from its base at a maximum takeoff weight of 190 metric tons (420,000 lb). The aircraft can be refuelled by Il-78 tankers.