Ambac Financial Group Inc reported a fourth-quarter loss of more than $2 billion on Wednesday, as the bond insurer set aside nearly $1 billion more for losses tied to residential mortgage debt.

Ambac, which has suffered large losses after guaranteeing billions of dollars worth of risky repackaged subprime mortgage bonds, posted a loss of $2.34 billion, or $8.14 a share.

That was narrower than the year-earlier loss of $3.27 billion, or $32.03 per share, which included record write-downs for credit derivatives positions linked to assets including mortgages.

Excluding special items, the company lost $6.79 per share in the most recent quarter. Analysts on average expected a loss of 68 cents per share, according to Reuters Estimates.

Ambac shares were down 6 cents at 95 cents in trading before the market opened.