NARA, July 9 (Reuters) - A steady stream of mourners on Saturday visited the scene of the bloody assassination of former Japanese Prime Minister Shinzo Abe's in the western city of Nara, an unusual act of political violence that has shocked the nation.

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

"I'm just shocked that this kind of thing happened in Nara," Natsumi Niwa, a 50-year-old housewife, said after offering flowers with her 10-year-old son near the scene of the killing at a downtown train station.

Abe, a conservative and architect of the "Abenomics" policies aimed at reflating the Japanese economy, inspired the name of her son, Masakuni, with his rallying cry of Japan as a "beautiful nation", Niwa said. "Kuni" means nation in Japanese.

Campaigning resumed on the final day of electioneering before polling for the upper house of parliament, which is expected to deliver victory to the ruling coalition led by Prime Minister Fumio Kishida, an Abe protege.

"A wave of sympathy votes now could boost the margin of victory," James Brady, vice president at advisory firm Teneo, wrote in a note. The Liberal Democratic Party, where Abe retained considerable influence, had already been expected to gain seats before the assassination.

Abe's death has raised questions about the security measures for public figures in Japan, where politicians commonly make direct appeals to voters outside train stations and supermarkets during campaigning season.

A scion of a political family who became Japan's youngest post-war premier, Abe was rushed to a Nara hospital following the shooting. He did not regain consciousness and was pronounced dead about five and a half hours after the late-morning attack.

Police are scrambling to establish details of the motive and method of Abe's killer.

A motorcade thought to be carrying the body of the slain politician left the hospital early on Saturday. It is thought to be heading for his Tokyo residence, local media reported.

Kishida spoke on Saturday with U.S President Joe Biden, who expressed his condolences and praised Abe's leadership, NHK reported.

Abe was key in the creation of the Quad grouping aimed at countering China's influence in the Indo-Pacific region. The other members, the United States, India and Australia, expressed shock at the assassination in a joint statement.

"We will honour Prime Minister Abe's memory by redoubling our work towards a peaceful and prosperous region," the statement said.