TORONTO (Reuters) - The Toronto Stock Exchange's main index tumbled more than 275 points to its lowest level in about a month on yesterday as renewed credit worries weighed on investors.

The S&P/TSX composite index fell 276.63 points, or 2.08 percent, to close at 13,005.09 in a broad-based sell-off.

"This credit problem rears its ugly head at least twice a week now and I think people are getting more and more nervous," said John Kinsey, portfolio manager at Caldwell Securities in Toronto.

"I think it's just simply more of the same."

The S&P/TSX 60 index of Canadian bluechips lost 16.62 points to end at 763.48.

The main index plunged more than 300 points before recovering slightly late in the day. Still, all but one of its 10 main groups finished in the red.

Telecoms were the lone bright spot, where BCE Inc. racked up gains after a Quebec court approved its C$34.8 billion buyout by private-equity investors and dismissed claims by bondholders who said the deal was unfair.

BCE rose C$1.92, or 5.4 percent, to end at C$37.72 while the sector added 0.26 percent as a whole.

The heavyweight energy and materials groups lost 1.59 percent and 4.23 percent, respectively. Financials shed 2.25 percent.

Among banks giving up ground were Bank of Montreal, which shed C$1 to finish at C$42.10 and the Royal Bank of Canada, which lost 71 Canadian cents to settle at C$45.40. Fairfax Financial lost C$14.48, or 5.2 percent, to finish at C$265.

Declining miners included Inmet Mining, which fell C$5.32, or 6.1 percent, to C$81.33. Zinc giant Teck Cominco dropped C$1.48 to finish at C$40.11.

Kinsey said one way to ride out the plunge that equity markets have been experiencing in recent weeks could be to keep a significant percentage of one's portfolio in cash.

"I think that you don't want to stand in an avalanche," he said. "You move to the sidelines."

Renewed credit jitters also rattled nerves on US markets on yesterday, with the Dow Jones industrial average falling 153.54 points, or 1.29 percent, to 11,740.15.

The tech-heavy Nasdaq ended 43.15 points lower, at 2,169.34.