The Mitsubishi Ki-20 was a Japanese attempt to copy and refine the German Junkers G38 large airliner for use as a covert bomber and was kept secret throughout the war. A total of 6 were built between 1932-35 and operated with the IJAAF intended to attack the forts at Manila Bay and also strikes against Siberia should Japan attack the USSR. But the license-built machines had to be modified to carry 11,023 lbs of bombs and 5x 7.7mm MGs were installed along with 1x 20mm cannon. The engines were upgraded to Junkers 204s at 4x 750 hp (3000 hp total)... but the plane would only have a top speed of 125 mph which made it slow and cumbersome in the air. Still, the Japanese conducted practice flights until 1940. After that, most were lost in air raids or eventually were scrapped as Japan proceeded with more modern bombers like the late Renzan and the projected strategic Fugaku to rival the B-29. They also had jet bomber projects courtesy of the Germans! Only one survived the war in a museum...

http://upload.wikimedia.org/wikipedia/commons/e/e0/Mitsubishi_Ki-20.jpg http://aviarmor.net/aww2/_photo_aircraft/f_jap/Mitsubishi%20Ki-20/ki-20_2.jpg http://farm5.staticflickr.com/4009/4631868628_13eb6bb106_z.jpg