TORONTO (Reuters) - Toronto's main stock index fell more than three percent yesterday as tumbling commodity prices rattled the resource-heavy index and knocked it to its lowest closing level in two weeks.

The market tumbled more than 100 points at the open and was never able to recover as prices for key Canadian exports such as oil and gold were hammered throughout the session.

"It's been red since they rang the bell this morning," said Bruce Latimer, a trader at Dundee Securities. "You've got gold down, oil down, commodities down and the Canadian dollar is down and that's going to take our market with it."

The slide was headlined by sharp sell-offs in the energy and materials sectors, which together make up about 40 percent of the overall index.

The materials group, which is home to gold-mining stocks, led the market lower with a 6.41 percent skid, followed by a 3.98 percent drop in the energy sector.

Weighing on gold-mining stocks was a four percent drop in gold prices to a one-month low as the US dollar rallied against the euro on expectations for an interest rate cut in the euro zone later this week.

Shares of Goldcorp fell six percent to C$30.40, while Barrick Gold Corp. shares dropped three percent to C$37.99, and Kinross Gold shares fell 3.45 percent to C$20.41.

The Toronto Stock Exchange's S&P/TSX composite index closed down 291.85 points, or 3.21 percent, at 8,793.33.

Toronto's key index had charged out of the gate in 2009 with a string of solid gains that had it up 5.76 percent midway through last week.

But a few losing sessions, mostly at the hands of lower commodity prices, have stripped it of all its gains and left it down two percent for the year.