All 10 of the main sectors ended in the red, with heavyweight financial, energy and materials stocks doing the most damage.

The Toronto Stock Exchange's S&P/TSX composite index <.GSPTSE> has hit record highs this year but started to stumble earlier in September as commodity prices come under pressure.

"It could definitely be general market fatigue" among investors, said Kevin Headland, a director in the portfolio advisory group at Manulife Asset Management. "It could very well be opportunistic profit-taking."

The index dropped 200.19 points, or 1.29 percent, to end the day at 15,265.35. The index recorded a 1.7 percent decline for the week.

"A market that starts to sell off can often be self-fulfilling as it hits other people's stop-loss trades and continues downward," Headland said.

Suncor Energy Inc (>> Suncor Energy Inc.) lost 2.5 percent to C$41.99, and Encana Corp (>> Encana Corporation) declined 2.5 percent to C$23.79.

"Energy has been the big drag this week, tied in to the decline in the price of oil we've seen," said Rick Hutcheon, president and chief operating officer at RKH Investments.

"We've come from the low $100s to the low $90s; that's a pretty big drop. The perception is that the world is well supplied with oil right now."

TransCanada Corp (>> TransCanada Corporation) bucked the trend, rising 0.9 percent to C$61.38 after saying its current corporate structure, asset base and financial strength are critical to its growth.

The stock had jumped on Thursday after Reuters reported U.S. hedge funds were eyeing the pipeline operator as a breakup candidate.

Hutcheon said energy producers would likely rebound, with gas players such as Encana leading the charge as winter approaches and refineries switch capacity to heating oil.

Banks piled on the downward pressure, which RKH's Hutcheon said could be a reaction to Scotland voting to stay within the United Kingdom. The sector is often considered more attractive when investors seek safety.

Royal Bank of Canada (>> Royal Bank of Canada) fell 1.6 percent to C$81.80, Toronto-Dominion Bank (>> Toronto-Dominion Bank) gave up 1.7 percent, to C$56.56, and Bank of Nova Scotia (>> The Bank of Nova Scotia) finished down 1.9 percent at C$71.56.

Miners also weighed, with Canadian Natural Resources (>> Canadian Natural Resources Limited) down 2.3 percent at C$44.07. First Quantum Minerals Ltd (>> First Quantum Minerals Limited) fell 4 percent to C$21.61 after it suspended operations at a mine in Mauritania.

(Reporting by Alastair Sharp; Editing by W Simon, J Benkoe and Jonathan Oatis)

By Alastair Sharp