A family of five - including three young children - found dead in a van in central Japan are believed to have been a suicide, a police official said on Friday.

The five - a man and a woman in their 30s and three boys aged five, seven and 10 - were found late on Thursday in the vehicle at a parking lot in Fujinomiya, Shizuoka prefecture, said the official at the Fujinomiya Police Department.

The five are believed to have died of carbon monoxide poisoning after burning charcoal pieces inside the vehicle - a not uncommon method of taking one's own life in Japan.

“We are investigating the case as a possible family suicide as they have also left a suicide note,” the police spokesman said.

Japan, with a population of about 128 million, has one of the world's highest suicide rates, according to the Organisation for Economic Co-operation and Development.

Every year more than 30 000 people take their lives in a country where suicide carries less of a stigma than in some western nations. - AFP