An impressive record. The Dutch merchant fleet did the same thing, IIRC. In fact, a Dutch freighter was at Pearl Harbor on December 7, 1941, and being armed, her gunners opened fire on the Japanese planes. I wish I could remember her name.
The Dutch were at war with Japan, Norway wasn't. Quite a few Norwegian sailors ended up in Japanese POW camps as they served the Allied war effort but I don't think they ever opened fire at Japanese ships.
This is only because Norway didn't have colony's in the "far east" like the Dutch Indies....that's the difference! We were just as Neutral before Germany invaded!
Actually, Holland was not officially at war with Japan on December 7th. Perhaps the merchantman's crew figured that they would be, so they might as well get in the first lick.
Bit off topic, but on the same lines. A Norwegian air force pilot who escaped the fall of Norway, and saw service in the RAF as a night fighter pilot, shot down a Italian CANT bomber in the Med theater. However some bright spark in the British War Office realised that Norway wasn't at war with Italy, so they reclassified his victory as over a Luftwaffe JU 88.