'Stunned, outraged': Joe Biden on ex-Japan PM Shinzo Abe's assassination

Abe was shot at about 11:30 a.m. local time in Nara, east of Osaka in Japan while giving an election campaign speech on the street.

"Above all, [Abe] cared deeply about the Japanese people and dedicated his life to their service. Even at the moment he was attacked, he was engaged in the work of democracy," Biden said in a statement released by the White House.

"While there are many details that we do not yet know, we know that violent attacks are never acceptable and that gun violence always leaves a deep scar on the communities that are affected by it. The United States stands with Japan in this moment of grief. I send my deepest condolences to his family," he said.

Former US President Donald Trump, who was close to Abe shared: "Few people know what a great man and leader Shinzo Abe was, but history will teach them and be kind," Trump said in a statement available to the media.

"He was a unifier like no other, but above all, he was a man who loved and cherished his magnificent country, he said"

Abe was Japan's longest-serving prime minister. He was 67.

The bullet hit him on the right side of his neck, according to officials in Tokyo. He was rushed to the hospital first by ambulance, then by medical helicopter.

Abe was declared dead at 5:03 p.m. local time, according to the head of Nara Medical University.

Doctors told a news conference that the former prime minister succumbed to the injury that caused excessive bleeding and the bullet pierced deep enough to reach his heart.

Police arrested Tetsuya Yamagami, a Nara resident in his 40s, in relation to the shooting, according to NHK, citing police sources. The assailant used a handmade gun and did not try to escape and is being held for questioning at Nara Nishi police station, it added.