According to [0] it was electromechanical rather electronic: "There were earlier electromechanical computers, the first being Konrad Zuse's Z3, completed in Berlin in 1941."

Interesting that all the quotes above start "the first" or "the world's first" followed by some very specific definition.

See also https://en.wikipedia.org/wiki/History_of_computing_hardware#... which does list the CSIRAC but I'm not sure which combination of options you need to get it to be "The world's fourth digital computer".