(Adds portfolio manager comment, updates prices to close)
* TSX ends down 263.33 points, or 1.92 percent, to 13,473.67
* Nine of the TSX's 10 main groups fall
By Solarina Ho and Alastair Sharp
TORONTO, Aug 21 (Reuters) - Canada's main stock index sank to its lowest in 18 months on Friday, capping a week of rapid retreat on persistently grim global sentiment following more disappointing data out of China.
Global equity markets plummeted toward their worst week this year, while the beating in commodities continued as data out of China showed manufacturing in the country was slowing at the fastest pace since the financial crisis in 2009.
The commodities-heavy TSX took another drubbing, with energy stocks falling 1.5 percent and materials sliding 2.9 percent. The hefty financials group, whose banks report quarterly results next week, fell 1.9 percent.
"There's not a lot of positive things that support the equity price," said Marcus Xu, a portfolio manager at M.Y. Capital Management Corp in Vancouver. "That's probably why people are getting a little panicked."
The Toronto Stock Exchange's S&P/TSX composite index closed down 263.33 points, or 1.92 percent, at 13,473.67. It lost almost 6 percent in the week, its worst weekly slump since September 2011.
Decliners outnumbered advancers by 224 to 21, and the index posted two new 52-week highs and 70 new 52-week lows.
"We're really breaking some really key levels. It's a sign that we're in a very severe correction," said John Johnston, chief strategist at Davis-Rea. "It's being driven by a continued slowdown in the global production cycle, which is so important for the demand for commodities."
He said weakness in emerging markets could drag the global economy into a recession.
Canadian Natural Resources fell 2.7 percent to C$26.80.
Crude prices suffered their longest losing streak since 1986 following the dismal Chinese data, which also sent copper prices down. U.S. oil futures settled down more than 2 percent to $40.45 a barrel after falling as low as $39.86. Three-month copper on the London Metal Exchange ended down 1.3 percent to $5,055 a tonne.
Of the index's 10 main groups, only telecoms were on higher ground, up 0.8 percent. All the remaining sectors fell more than 1 percent, including consumer staples, which slumped 2.7 percent.
Convenience store operator Alimentation Couche-Tard lost 5.9 percent to C$54.58.
Royal Bank of Canada fell 1.7 percent to C$72.80 and was among the biggest drags on the TSX. Manulife Financial Corp was down 4.1 percent at C$20.46.
In corporate news, Eldorado Gold Corp shares plunged 14 percent to C$4.48 after the company said on Thursday it suspended mining activities in northern Greece. (Reporting by Solarina Ho; Editing by James Dalgleish)