TOKYO - THE parents of the suspect behind a stabbing rampage in Tokyo that left seven people dead wept and bowed as they offered a heartfelt apology, with his mother collapsing to the ground in grief.

'We are terribly sorry for the people who lost their lives and were injured by what our son did,' said the 49-year-old father of suspect Tomohiro Kato.

'No matter how many times we apologise, we cannot apologise enough,' the father added, bowing deeply many times before television cameras in front of their house in the northern town of Aomori late on Tuesday.

To respect the parents' privacy, media agreed to pixelate their faces and not give their first names.

The father, clad in a short-sleeved chequered shirt and black trousers, has previously been identified as a banker.

Media reports have said their son, who in the course of a few years went from studying at Aomori's top high school to working at an auto parts factory, would beat his own mother as he failed to live up to her expectations.

In Japan's deadliest crime in seven years, Kato drove a rented two-tonne truck Sunday into Tokyo's crowded district of Akihabara, which is the hub of Japan's comic-book and video-game subculture.

He swerved the vehicle into pedestrians, jumped out and ran into the crowds brandishing a survival knife in one hand and a smaller knife in the other. He wounded 17 people before he was overpowered by police.

Four died from stab wounds and three others were killed by the truck. -- AFP