Japanese officials scrambled to calm market fears of financial crisis Tuesday after the investment bank Lehman Brothers filed for bankruptcy.

The bank filed for bankruptcy protection in the United States on Monday and its Japanese unit reportedly did the same Tuesday in Japan.

Japan's central bank issued a statement vowing to take measures to maintain stability in the country's financial markets, and the financial services minister said the impact on the Japanese financial institutions was limited.

"The Bank of Japan will closely watch development surrounding the latest U.S. financial institutions and its impact, and will continue to take appropriate measures to maintain smooth settlement and stability in the financial market," Bank of Japan Gov. Masaaki Shirakawa said in a statement.

Financial Services Minister Toshimitsu Motegi also said the "So far, we haven't confirmed any signs that Japanese financial institutions are seriously affected." Motegi added that officials will "raise alert levels" to monitor the situation closely.

Lehman Brothers Holdings Inc., filed for Chapter 11 bankruptcy protection from its creditors on Monday. The 158-year-old investment bank was crippled by $60 billion in soured real-estate holdings and was unable to find an investment partner to throw it a lifeline.

It's Japanese unit also filed for bankruptcy protection at a Tokyo court Tuesday, Kyodo News agency reported.

Lehman Brothers Japan Inc. sought protection from creditors under the Japanese civil rehabilitation law, Kyodo said, quoting unidentified officials. Court officials refused to confirm the report, citing privacy reasons.

Lehman Brothers Japan officials were not immediately available for comment Tuesday.

On Monday, Japan's financial watchdog ordered Lehman's Japan unit to suspend operations after the U.S. investment bank filed for bankruptcy.

The agency said in a statement that Lehman's Japanese operations — except those that involve returning assets to customers — would be suspended for 12 days starting Monday.

The agency issued a separate statement ordering Lehman's Japanese unit to take "full measures" to protect investors and assets after it filed for bankruptcy. The Japanese watchdog also ordered Lehman Brothers Japan Inc. to keep certain assets in the country.

Lehman opened its first office in Tokyo in 1973, and its operations in Tokyo are one of its key global businesses after New York and London, according to its Web site.

Citing data from the Japanese financial watchdog, Kyodo News agency said Lehman's Japanese unit manages about 1.2 trillion yen — or $11.4 billion — worth of assets from investors.

Lehman's failure comes as Bank of America announced it will snap up Merrill Lynch & Co. Inc. in a $50 billion all-stock deal and reports in the Wall Street Journal and The New York Times said that insurance giant American International Group was seeking $40 billion in emergency funds to help it avoid a credit rating downgrade.