Shinzo Abe shot: What we know so far about the attacker

Read: Video shows the moment Shinzo Abe was shot at while delivering speech

Abe, 67, who was campaigning for elections to Japan parliament's upper house, collapsed, bleeding from the neck.

Bystanders rushed to help him. He was hospitalised, with reports saying he was showing no vital signs,

Abe is Japan's longest-serving prime minister. He was in office for one year in 2012 and then again from 2012 to 2020. He had resigned due to health reasons.

World leaders expressed outrage over the attack on Abe and prayed for his recovery.

"Deeply distressed by the attack on my dear friend Abe Shinzo," India's Prime Minister Narendra Modi tweeted. "Our thoughts and prayers are with him, his family, and the people of Japan."

Australian Prime Minister Anthony Albanese wrote: "Shocking news from Japan that former PM Shinzo Abe has been shot -- our thoughts are with his family and the people of Japan at this time."

The United States' ambassador to Japan described Abe as an "outstanding leader" and  "unwavering ally".

"The US Government and American people are praying for the well-being of Abe-san, his family and people of Japan," Rahm Emanuel said.

Meanwhile, Japan's incumbent Prime Minister Fumio Kishida described the attack on Abe as barbaric.

"I pray that former prime minister Abe will survive," Kishida was quoted ad saying by news agency AFP. "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."

(With inputs from AFP)