TORONTO (Reuters) - The Toronto Stock Exchange's main index ended sharply lower yesterday as it suffered the double whammy of weak resource issues and further worries over the global credit crisis.

Taking its cue from international markets, the TSX skidded more than 300 points immediately after the opening bell in a steep selloff following the purchase of Bear Stearns by JP Morgan Chase for the fire sale price of $2 a share.

Worries over how deeply a stumbling US economy will infect the rest of the world and whether a slowdown will slash global demand for resources drove Toronto's heavyweight energy and financial sectors down 2.8 percent and 2.5 percent respectively.

Shares of banks and resource companies were among the biggest weights on the index, with National Bank of Canada falling C$1.54, or 3.4 percent, to C$44.39 and Canadian Natural Resources down C$3.07, or 4.2 percent, at C$69.65.

The energy sector was also hurt by a decline in the price of oil, which retreated $4.53 to $105.68 a barrel, while investors traded in futures in favor of cash.

The S&P/TSX composite index closed down 300.69 points, or 2.27 percent, at 12,952.15 with all but one of its 10 main groups in the negative. The index managed to gain back some losses after falling by more than 400 points in the afternoon.

The materials sector, home to resource shares, tumbled amid worries over global demand, falling 1.8 percent. Potash Corp of Saskatchewan fell C$3.69, or 2.3 percent, to C$154.45 while Inmet Mining was off C$3.83, or 4.5 percent, at C$81.71.

The Toronto benchmark's strong weighting in resources, which make up nearly half the index, kept it much more deeply below water than its U.S. counterparts.

The small health sector was the lone group with any upward momentum, jumping 7.1 percent with help from strong gains by QLT Inc and Cardiome Pharma.

QLT surged C$1.29, or 55.6 percent, to C$3.61 after it said it will continue with plans to divest its topical acne treatment after the US Food and Drug Administration lifted key blood monitoring requirements.

Cardiome jumped C$2.02, or 32.3 percent, at C$8.27 after it released positive interim clinical results for its oral heart drug and said it was looking at possible partnerships and other strategic alternatives.