Japan's former premier Shinzo Abe was fighting for his life on Friday after being shot at a campaign event, the prime minister said, condemning the "absolutely unforgivable" attack.
The shooting of the country's best-known politician comes despite Japan's strict gun laws and with campaigning under way ahead of upper house elections on Sunday.
"Former prime minister Shinzo Abe was shot in Nara and I have been informed he is in a very grave condition," Prime Minister Fumio Kishida told reporters after arriving in Tokyo by helicopter from the campaign trail.
"I pray that former prime minister Abe will survive," the visibly emotional leader said.
"It is a barbaric act during election campaigning, which is the foundation of democracy, and it is absolutely unforgivable. I condemn this act in the strongest terms."
The attack took place shortly before noon in the country's western region of Nara, and "one man, believed to be the shooter, has been taken into custody", government spokesman Hirokazu Matsuno earlier told reporters.
Kishida said "no decision" had been made on the election, though several parties announced their senior members would halt campaigning in the wake of the attack.
Abe, 67, had been delivering a stump speech with security present, but spectators were able to approach him fairly easily.
Footage broadcast by NHK showed him standing on a stage when a loud blast was heard with smoke visible in the air.
As spectators and reporters ducked, a man was shown being tackled to the ground by security.
Local media identified the man as 41-year-old Tetsuya Yamagami, citing police sources, with several media outlets describing him as a former member of the Maritime Self-Defense Force, the country's navy.
He was wielding a weapon described by local media as a "handmade gun", and NHK said he told police after his arrest that he "targeted Abe with the intention of killing him".
'A large bang'
Witnesses at the scene described shock as the political event turned into chaos.
"He was giving a speech and a man came from behind," a young woman told NHK.
"The first shot sounded like a toy bazooka. He didn't fall and there was a large bang. The second shot was more visible, you could see the spark and smoke," she added.
"After the second shot, people surrounded him and gave him cardiac massage."
Abe was bleeding from the neck, witnesses said and photographs showed. He was reportedly initially responsive but subsequently lost consciousness.
Officials from the local chapter of Abe's Liberal Democratic Party said there had been no threats before the incident and that his speech had been announced publicly.
The attack prompted international shock.
"This is a very, very sad moment," US Secretary of State Antony Blinken told reporters at a G20 meeting in Bali, saying the United States was "deeply saddened and deeply concerned".
Thailand's Prime Minister Prayut Chan-O-Cha was "very shocked" at Abe's shooting, while Indian Prime Minister Narendra Modi said he was "deeply distressed" by the news.
'Profoundly sad and shocking'
Abe, Japan's longest-serving prime minister, held office in 2006 for one year and again from 2012 to 2020, when he was forced to step down due to the debilitating bowel condition ulcerative colitis.
He is a hawkish conservative who pushed for the revision of Japan's pacifist constitution to recognise the country's military and has stayed a prominent political figure even after his resignation.
Japan has some of the world's toughest gun-control laws, and annual deaths from firearms in the country of 125 million people are regularly in single figures.
Getting a gun licence is a long and complicated process for Japanese citizens, who must first get a recommendation from a shooting association and then undergo strict police checks.
Japan has seen "nothing like this for well over 50 to 60 years", Corey Wallace, an assistant professor at Kanagawa University who focuses on Japanese politics, told AFP.
He said the last similar incident was likely the 1960 assassination of Inejiro Asanuma, the leader of the Japan Socialist Party, who was stabbed by a right-wing youth.
"But two days before an election, of a (man) who is so prominent... it's really profoundly sad and shocking."
He noted, too, that Japanese politicians and voters are used to a personal and close-up style of campaigning.
"This could really change."