On 7 February 2013, two Su-27s briefly entered Japanese airspace off Rishiri Island near Hokkaido, flying south over the Sea of Japan before turning back to the north. Four Mitsubishi F-2 fighters were scrambled to visually confirm the Russian planes, warning them by radio to leave their airspace. A photo taken by a JASDF pilot of one of the two Su-27s was released by the Japan Ministry of Defense. Russia denied the incursion, saying the jets were making routine flights near the disputed Kuril Islands. In another encounter, on 23 April 2014 an Su-27 nearly collided with a United States Air Force Boeing RC-135U over the Sea of Okhotsk.