The 67-year-old appeared to be in a state of cardiac arrest, according to the network and Kyodo news agency. Shots were heard and a cloud of white smoke was seen as Abe delivered a campaign stump speech outside a train station on Friday, NHK said.
An NHK reporter on the scene said they could hear two consecutive bangs during Abe’s speech.
Abe served two terms as prime minister to become Japan’s longest-serving prime minister, before resigning in 2020 due to ill health.
But he has remained a dominant presence over the ruling Liberal Democratic Party (LDP) and controls one of its main factions.
His protégé, Prime Minister Fumio Kishida, faces a Senate election on Sunday, in which analysts say he hopes to emerge from Abe’s shadow and determine his premiership.
Abe is best known for his signature “Abenomics” policy of bold monetary easing and fiscal spending.
He also boosted defense spending after years of declines and expanded the military’s ability to project power abroad.
In a landmark shift in 2014, his administration reinterpreted the post-war, pacifist constitution to allow troops to fight overseas for the first time since World War II.
The following year, legislation ended a ban on exercising the right of collective self-defense or defending a friendly country under attack.
However, Abe did not achieve his long-held goal of revising the United States-drafted constitution by writing the self-defense forces, as the Japanese military is known, in the pacifist Article 9.
He was instrumental in winning the 2020 Olympics for Tokyo and harbored a desire to lead the Summer Games, which were postponed by a year to 2021 due to the Covid-19 pandemic.
Abe first took office in 2006 as Japan’s youngest prime minister since World War II. After a year ravaged by political scandals, voter outrage over lost pension records and election abuse for his ruling party, Abe stopped citing ill health.
In 2012, he became prime minister again.
Abe comes from a wealthy political family that includes a father of a secretary of state and a great-uncle who was prime minister.