Former Japanese prime minister Shinzo Abe has been while giving a speech in the western city of Nara, according to reports.
Public broadcaster NHK said he appeared to be in a state of cardiac arrest.
The channel said shots were heard and a white puff of smoke was seen as Mr Abe made a campaign speech outside a train station.
A reporter on the scene said they could hear two consecutive bangs during the speech.
NHK aired footage showing Mr Abe collapsed on the street, with several security guards running toward him.
A spokesman for Nara City Fire Department said he was in cardiopulmonary arrest before he was taken to hospital.
According to reports a man was arrested at the scene.
Mr Abe served two terms as prime minister to become Japan’s longest-serving premier before stepping down in 2020 citing ill health.
But he has remained a dominant presence over the ruling Liberal Democratic party (LDP) party, controlling one of its major factions.
His protege, Prime Minister Fumio Kishida, faces an upper house election on Sunday in which analysts say he hopes to emerge from Mr Abe’s shadow and define his premiership.