TOKYO, July 9 (Reuters) - Campaigning in Japan was due to resume on Saturday in the final day of electioneering before polling for the upper house of parliament, even as the country reeled from the killing of former Prime Minister Shinzo Abe by a gunman in an unusual act of political violence.

Abe, Japan's longest serving modern leader, was gunned down while making a campaign speech in the city of Nara on Friday morning by an unemployed 41-year-old man, in an act decried by the political establishment as an attack on democracy itself.

Politicians pledged to continue campaigning ahead of Sunday's poll, which is expected to deliver victory to Japan's ruling coalition, while police scrambled to establish the motive and method of Abe's killer.

A scion of a political family who became Japan's youngest post-war premier, Abe was rushed to a Nara hospital following the shooting before being pronounced dead in the late afternoon.

A vehicle thought to be carrying the body of the slain politician left the hospital before 6 a.m. (2100 GMT on Friday), NHK reported, and was thought to be heading for his Tokyo residence. (Reporting by Tokyo newsroom; Editing by Sandra Maler)