Aucklanders were alarmed in the middle of World War II when "small" bombs fell from a plane on a summer Saturday afternoon.

Two suburbs, Birkenhead and Herne Bay, on opposite sides of the Waitematā Harbour, were hit by the seemingly accidental bombing in quick succession about 3pm on December 11, 1943.

No one was injured by the so-called "practice" bombs. Homes were narrowly missed but none was damaged. However, the bombs, which fell on to roadways, blew craters through the surface and threw debris into the air.

Witnesses likened the explosion they heard to the sound of a car backfiring.