In its filing in a Tokyo district court, the midsize company listed debts of 269.5 billion yen, or $2.7 billion, Kyodo news service reported.

Company officials sought recourse to an 8-year-old law allowing courts to order assets of troubled financial institutions to be protected, the report said.

Japan's Finance Minister Shoichi Nakagawa said the company's failure was an isolated event.

"The company used proceeds from high-yielding securities to cover losses from high-cost insurance operations," Nakagawa said in a statement.

Yamato's problems stem from investment losses in subprime mortgage-related bonds and other securities whose prices have collapsed, company officials said.

"We attempted to strengthen our risk management, but we have come to this regrettable outcome," said company President Takeo Nakazono, the Daily Telegraph of London reported.

Yamato is the eighth Japanese life insurance company to fail since the end of World War II, Kyodo said.

At the end of March, the company had a workforce of more than 1,000 had 170,000 individual insurance contracts, and its assets totaled 283.1 billion yen, or $2.84 billion.