US banking giant Citigroup reported Friday a first-quarter net loss of 5.1 billion dollars, hurt by at least 12 billion dollars in write-downs amid soured subprime investments and rising credit costs.

Earnings per share were a negative 1.02 dollars, a steeper than the 95-cent loss that most analysts' forecast.

It was the second consecutive quarterly loss for the banking titan, hammered by the subprime, or high-risk, mortgage crisis stemming from the worst US housing slump in decades and signs of recession in the world's biggest economy.

Citigroup is now the US bank hardest hit by the subprime crisis that erupted in August, wreaking havoc on financial markets and leading to a credit squeeze that is damping growth in the global economy.

The bank has taken more than 30 billion dollars in write-downs, more than peer Merrill Lynch, which reported Thursday a net loss of two billion dollars and write-downs of up to nine billion dollars.

Citigroup said the first-quarter net loss was mainly driven by fixed-income results and higher consumer credit costs.

Citigroup took six billion dollars in pre-tax write-downs and credit costs on subprime-related direct exposures, 3.1 billion dollars on funded and unfunded highly leveraged finance commitments, a downward credit value adjustment of 1.5 billion dollars related to exposure to monoline, or municipal bond, insurers, and 1.5 billion dollars on auction rate securities inventory.

It also reported a 3.1-billion-dollar increase in credit costs in its global consumer business, including a loss of 1.7 billion dollars and a reserve for bad loans of 1.3 billion dollars.

Vikram Pandit, Citi chief executive, said the financial results "reflect the continuation of the unprecedented market and credit environment and its impact on our historical risk positions."

Pandit said that during the first quarter, valuations of the bank's subprime-related exposures in fixed-income markets and leveraged finance assets had further declined and credit costs in its consumer lending businesses had increased.

"Despite the negative factors in the broader markets, we continue to see strong momentum throughout the organization with robust volumes in many of our products and regions," he said.

"We have taken decisive and significant actions to strengthen our balance sheet, including over 30 billion dollars of capital raised during December and January," he said.

Pandit noted that the bank recently reorganized its businesses along regional and product lines.

"As we move into the second quarter and beyond, we will continue to divest non-strategic assets and allocate capital to the products and regions that will drive increased revenues, enhance the value of our franchise, and ultimately, maximize shareholder value," he said.

Citigroup announced in January a fourth-quarter net loss of 9.83 billion dollars, dragged down by soured mortgage investments.