Japanese police have found the bodies of nine people who apparently committed suicide after meeting via special suicide sites on the internet.
Seven bodies were found inside a van in the Saitama mountains
A police spokesman said seven young people were found in a van in the Saitama mountains to the west of Tokyo.
Minutes later, two women were found dead in a car south of Tokyo, in another apparent suicide pact.
Japan has recently seen a wave of internet-linked suicides, as people seek companions to die with.
More than 34,000 Japanese took their own lives in 2003, according to the National Police Agency - an increase of more than 7% from the previous year.
Economic difficulties and an increasing sense of isolation among Japanese youth are believed to be contributing to the rise.
A small but growing number of suicide attempts are being made by people brought together through the internet.
Analysts have speculated that group suicide may mitigate the inherent loneliness of taking one's life alone.
The BBC's Tokyo correspondent says dozens of suicide websites have appeared in recent years offering advice to those who plan to kill themselves.
The three women and four men who died in Saitama were all reportedly in their teens or early 20s.
It was probably the largest group suicide in Japan so far, police said.
This group and the two women found in Kanagawa are believed by police to have died from carbon monoxide poisoning as a result of charcoal burners in their cars.
"We believe they all died after inhaling carbon monoxide from the charcoal," a police spokesman said of the seven found in Saitama. "We believe they got acquainted through the internet."
"We found no traces of violence that could have otherwise led to their deaths," he said.
Investigators had yet to establish whether the two cases were related.
Our correspondent says suicide has become a widely discussed topic on many websites, and there is even a guidebook to the best places to kill yourself.
The authorities have talked about closing down or regulating the websites.
But organisers argue that they offer a compassionate service to those who have given up all hope of the future.
Increasing numbers of young people in Japan are feeling alienated by modern life. Several thousand are termed "hikikomori" - recluses who never leave their room, finding entertainment only on the internet.