At least nine people were injured, one seriously, when a auto deliberately plowed into crowds celebrating New Year's Eve in a central part of Tokyo, according to police.
It is not yet clear whether he was referring to a specific execution or the capital punishment system in Japan. "Really scary, isn't it?" one bystander told NHK. "By the time I reached the exact place, paramedics were already there helping people", he said.
A police spokesman said the driver had been detained but has not given out any further details on the identity of the suspect.
Images showed crowds flocking to the shrine on New Year's Day, despite the incident just hours earlier.
Police said the man was in his 20s and had an "intent to murder".
Police said eight people were hurt by the vehicle when it auto drove into the crowd, including a young male who was taken to hospital in critical condition, according to Japanese news agency Kyodo.
According to local media, Kusakabe hit a total of eight people and assaulted another on the street, which was closed to traffic for the New Year celebrations.
Some media reports said the man had linked the attack to the executions in July of 13 members of the Aum Shinrikyo or Aum Supreme Truth cult, who were responsible for a 1995 sarin gas attack on the Tokyo subway.
"I heard the man say, As long as you keep bombing these countries this is going to keep happening", the producer, Sam Clack, told BBC 5 Live radio. "I looked down and saw he had a kitchen knife with a black handle with a 12-inch (30cm) blade". "It was very very scary", Clack said.
The victims of the New Year's attack, including one teenager, are being cared for in nearby hospitals.
Shoko Asahara, the leader of the Aum Shinrikyo, was the first of 13 cult members to be hanged in July for the subway attack that killed 13 people and poisoned more than 6000 others.
In Indonesia, a landslide after heavy rain on Monday left at least nine dead in West Java.