HOUSTON (AP) -- Oil refiner Frontier Oil Corp. on Thursday posted a third-quarter loss driven by continued weak demand and squeezed refining margins.

Crude oil prices have climbed steadily since March, but gasoline prices haven't matched the pace, hurting margins for refiners.

Further damage came as demand remained sluggish in the third quarter amid swelling inventory levels, the company said.

"This period of low refining margins continues to challenge domestic refiners, evidenced by recent capacity exiting the system," said Frontier CEO Mike Jennings.

The company reported a loss of $15.1 million, or 15 cents per share, compared with earnings of $72.3 million, or 70 cents per share, during the same period last year.

Results include one-time gains of 11 cents per share and a penalty of 7 cents per share. Excluding special items, the company's adjusted loss totaled 19 cents per share.

Analysts polled by Thomson Reuters estimated a loss of 15 cents per share, on average. Analysts typically exclude one-time items.

Revenue declined 45 percent to $1.2 billion, down from $2.2 billion in the prior-year period. Analysts forecast an average revenue of $1.26 billion.

Shares of Frontier fell 20 cents to $13.60 in midday trading.