Four men and three women were found stabbed to death in two houses at Kakogawa near the Japanese port city of Kobe today, police said.
Domestic media said a 47-year-old man had been detained in connection with the killings after crashing as he attempted to flee the scene by car.
The man is also thought to have set fire to a neighbouring house, burning it to the ground, Kyodo news agency said, adding that other people had been injured in the incident.