Mr Abe was shot at twice while he was giving a speech in the southern city of Nara on Friday morning.
Japan's former prime minister Shinzo Abe has died in hospital after he was shot at a political campaign event, say local media.
Mr Abe was shot at twice while he was giving a speech in the southern city of Nara on Friday morning, BBC reports.
He immediately collapsed and was rushed to the nearest hospital. Pictures taken at the scene showed him bleeding.
Security officials at the scene tackled the gunman, and the 41-year-old suspect is now in police custody.
In an emotional press conference earlier, prime minister Fumio Kishida told reporters that Mr Abe was in a "very grave condition".
"Currently doctors are doing everything they can," said Mr Kishida who appeared to be holding back tears, adding that he was "praying from his heart" that Mr Abe would survive.
He also condemned the attack, saying: "It is barbaric and malicious and it cannot be tolerated."
The Fire and Disaster Management Agency confirmed that Abe had a bullet wound on the right of his neck, and also suffered subcutaneous bleeding under the left part of his chest.
It is unclear if both shots hit him, or if a bullet hit him on the neck and travelled elsewhere.
National broadcaster NHK said Abe was "conscious and responsive" while he was transported to the hospital, citing police sources.
But it also quoted a senior member of Mr Abe's party as saying the 67-year-old's situation was "worrisome". Mr Abe's younger brother told reporters that the former PM was receiving a blood transfusion.
Ex-Tokyo governor Yoichi Masuzoe had earlier said in a tweet that Mr Abe was in a state of cardiopulmonary arrest. The term is often used before a death is officially confirmed in Japan.
Mr Abe was giving a stump speech for a political candidate in Nara at a road junction when the attack happened.
Eyewitnesses said they saw a man carrying what they described as a large gun and firing twice at Mr Abe from behind.
Security officers detained the attacker, who made no attempt to run, and seized his weapon which was reportedly a handmade gun.
The suspect has been identified as Nara resident Tetsuya Yamagami. Local media reports say he is believed to be a former member of Japan's Maritime Self-Defense Force, Japan's equivalent of a navy.
Mr Abe's speech came as part of a campaign for his former party, the Liberal Democratic Party, as upper house elections in Japan are due to take place later this week.
Ministers across the country were later told to return to Tokyo immediately, according to local reports.
On Japanese social media, the hashtag "We want democracy, not violence" was trending, with many social media users expressing their horror and disgust towards the incident.
Gun violence is very rare in Japan, and guns are extremely difficult to own. Political violence is also extremely rare.
Mr Abe did have a team of security police with him. But it appears the shooter was still able to get to within a few meters of Mr Abe without any sort of check, or barrier.
The shooting of such a prominent figure is profoundly shocking in a country that prides itself on being so safe.
Mr Abe, who was Japan's longest-serving prime minister, held office in 2006 for a year and then again from 2012 to 2020, before stepping down citing health reasons.
He later revealed that he had suffered a relapse of ulcerative colitis, an intestinal disease.
While he was in office, he pushed hawkish policies on defence and foreign policy, and has long sought to amend Japan's pacifist post-war constitution.
He also pushed for an economic policy that came to be known as "Abenomics", built on monetary easing, fiscal stimulus and structural reforms.