Former Japanese prime minister Shinzo Abe lies on the ground after apparent shooting during an election campaign for the July 10, 2022 Upper House election, in Nara, western Japan July 8, 2022. in this photo taken by Kyodo. (Mandatory credit Kyodo via REUTERS)

Chief Cabinet Secretary Hirokazu Matsuno said he did not know Abe's condition. Kyodo news agency and NHK said Abe, 67, appeared to be in a state of cardiac arrest when taken to hospital.

Authorities have arrested one man who appeared to have shot Abe, 67, in the back.

Abe served two terms as prime minister to become Japan's longest-serving premier before stepping down in 2020 citing ill health.

But he has remained a dominant presence over the ruling Liberal Democratic party (LDP) party, controlling one of its major factions.

Abe has been best known for his signature “Abenomics” policy featured bold monetary easing and fiscal spending.

He also bolstered defence spending after years of declines and expanded the military’s ability to project power abroad.

In a historic shift in 2014, his government reinterpreted the postwar, pacifist constitution to allow troops to fight overseas for the first time since World War Two.

Abe first took office in 2006 as Japan’s youngest prime minister since World War Two.