"Former prime minister Abe died at a hospital in Kashihara city, Nara, where he was receiving medical treatment. He was 67,"  said a senior member of Abe's Liberal Democratic Party, according to local reports.

Earlier on Thursday, Prime Minister Fumio Kishida told reporters said, "It is absolutely unforgivable. I condemn this act in the strongest terms." On hearing the news, Kishida left his campaign trail and rushed to Tokyo.

Kishida arrived at the Prime Minister's office at 2:30 p.m. local time by helicopter from Yamagata Prefecture where he was campaigning for the upcoming Upper House election and later met the press.

Chief cabinet secretary Hirokazu Matsuno said a man believed to be the shooter has been taken into custody.

According to local media said citing police sources that the man has been identified as 41-year-old Tetsuya Yamagami.

"He was giving a speech and a man came from behind," a young woman at the scene told NHK.

"The first shot sounded like a toy. 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, 67, was also campaigning for the ruling Liberal Democratic Party in the city of Nara in western Japan when he was shot from the back. He collapsed after a second shot, witnesses said.

Abe reportedly had no vital signs after being shot on the streets of Nara.

The incident happened around 11.30 am local time, shortly after Abe began to speak. Video footage going viral on social media appears to show security guards at the event apprehending someone.

Sources with the investigation told NHK that a gun seized at the scene appeared to be handmade.

Abe, Japan's longest-serving prime minister, held office in 2006 for one year.

He again assumed office from 2012 to 2020, when he was forced to leave office due to the debilitating bowel condition ulcerative colitis.