BNP Paribas, France's biggest listed bank, has reported a 50% fall in profit for the final three months of 2011, after taking further losses on its Greek debt holdings.

It reported net income of 765m euros ($1bn; £641m) for the quarter, after writing down its Greek assets by a further 567m euros.

The bank said it had now written down the value of its Greek debt by 75%.

For 2011 as a whole, net income was down 22.9% to 6bn euros.

Despite the sharp fall in fourth quarter profits, BNP's results were better than analysts' expectations and quarterly revenues of 9.69bn euros were also stronger than forecast.