Struggling US brokerage firm MF Global filed for bankruptcy Monday, after confidence in the firm was shattered by a string of losses from European public debt holdings.

The firm filed for Chapter 11 bankruptcy protection in a Manhattan bankruptcy court, making it the first major US casualty from the European debt crisis.

While MF Global is well-known on Wall Street, it is not thought to be so interconnected that its collapse could trigger a crash like that seen in the wake of the Lehman Brothers bankruptcy in 2008.

But attention immediately turned to JPMorgan Chase and subsidiaries of Deutsche Bank, after MF's bankruptcy filing showed those firms to be the firm's two biggest creditors.

JPMorgan was said to have a claim of over $1.2 billion with MF linked to bond holdings, while Deutche Bank had a claim of over $1.0 billion.

Shares in JPMorgan fell 3.3 percent on the news while Deutsche Bank's US-listed shares fell 8.7 percent.

Shares in MF -- which had reported $41 billion in assets at the end of September -- were halted on the New York Stock Exchange early Monday in anticipation of the move.

Ahead of the bankruptcy filing, Chris Low of FTN Financial wrote that MF's downfall would be "the biggest US casualty so far in the European sovereign crisis."

"Hopefully, the firm's situation is unique. (Chief executive Jon) Corzine's bet on sovereign debt is what got the firm in trouble. According to regulators, other, bigger US entities are not exposed."

According to figures from bankruptcydata.com, MF's filing is the eighth largest US bankrupcty in the last 30 years.

Lehman, the largest, had $691 billion in assets at the time of its collapse.

The Financial Times and The Wall Street Journal earlier reported MF was to issue the filing as part of a plan to sell off assets to Interactive Brokers Group, although it was still not certain that deal would go through.

There was no comment from Interactive Brokers early Monday.

According to the bankruptcy filing, MF Global has 25,000-50,000 creditors, and $100 to $500 million in assets.