Former Japanese prime minister Shinzo Abe suffered a heart failure after being shot in western Japan's Nara, where he was making a campaign speech for the parliament's upper house election to be held on Sunday.

Due to the sensitive time, the incident has raised suspicions of a political assassination. According to Japanese media NHK, Abe was shot from the back and collapsed during his speech.

Japanese media said Abe was apparently bleeding and in a state of cardiopulmonary arrest - a term often used in Japan before death is confirmed.

The attacker has been arrested and the case is under investigation by the local police. Analysts described the incident as the biggest political incident in Japanese politics after World War II.

Xiang Haoyu, a research fellow at the China Institute of International Studies, told the Global Times on Friday that the shooting comes at a sensitive time ahead of the upper house election, so political motives cannot be ruled out.

Although Abe had been the longest-serving Japanese prime minister, there are mixed opinions on him in Japan, and anti-Abe public opinion always existed,

including dissatisfaction with the widening gap between the rich and the poor caused by Abenomics, and disgust with his forced adjustment of military and security policies, Xiang said.

He noted that political assassinations have been carried out by Japan's radical left and right since World War II.

However, after the Cold War, as the political structure of left-right camp rivalry in Japan collapsed, extreme political activities decreased.

Although Japan's politics have been calm on the surface in recent years and the ruling status of the Liberal Democratic Party (LDP) is stable,

populist and other extreme ideas are still surging against the background of a long-term economic downturn and deep-seated difficulties in national development, experts said.

"Japan is well-known for its good public security and strict control of firearms, but in recent years, there are still vicious public security incidents,

which is also related to the stagnation of economic and social development in Japan and the suppression of social thought," Xiang said.

"Such violence should be strongly condemned, but Japan should also reflect on whether there is a danger of polarization in its domestic politics."