TORONTO (Reuters) - Toronto's main stock index fell to its lowest level in five weeks yesterday as global economic woes boosted the US dollar, weighing on commodity prices and the index's hefty resource sectors.

A strong US dollar, lifted in part by concerns about sovereign debt problems in Ireland and other European economies, helped drag oil prices down more than three percent to below $83 a barrel as investors cut their exposure to commodities.

Canadian Natural Resources fell 2.2 percent to C$38.70, while Suncor Energy also gave back 2.2 percent at C$33.67. TransCanada Corp. sank 2.6 percent to C$36.

The three big energy companies were the most influential movers on the downside. The broader energy group was down 1.8 percent.

"The market has become somewhat jittery that what happened to Greece might happen to Ireland, too. The market is basically telling us we don't like these uncertainties," said Sid Mokhtari, market technician and director, institutional equity research, CIBC World Markets.

Apart from euro zone debt concerns, investor sentiment was also bruised by worries over fiscal tightening by China.

And in US economic data, core producer prices recorded their largest fall in more than four years in October and industrial output was flat. The readings underscored concerns at the Federal Reserve about low inflation amid moderate economic growth.

The Toronto Stock Exchange's S&P/TSX composite index finished the day down 133.18 points, or 1.05 percent, at 12,602.23. Nine of the index's 10 main groups were lower, with telecoms the lone sector in the black. It was up 0.5 percent.

The index slid to a low of 12,501.82, its lowest level since mid-October and near its 50-day moving average, a key technical level that, if breached, could signal further losses, said Mokhtari.

The materials group, home to mining and fertiliser companies, was down 1.6 percent. Cameco Corp., slumped 4.5 percent to C$34.30, while Teck Resources was off 2.4 percent at C$48.16. NovaGold Resources Inc tumbled 3.6 percent to C$13.76.

Copper prices skidded five percent on euro zone jitters and China tightening fears, while gold tumbled on a rallying greenback.