Japan's Mitsubishi UFJ Securities Holdings said on Wednesday its loss related to an unnamed US client was estimated around 270 million dollars.
It had flagged a potential loss of around 300 million dollars a day before.
The company said the loss will be reflected in the first quarter of the fiscal year starting in April.
Losses are also likely at leading Japanese brokerage Nomura Holdings, as well as Switzerland's Credit Suisse, all involving the same US firm.
Some media reported losses at US investment firm Archegos Capital Management triggered the liquidation of positions, leading to potential losses at the financial companies.