The Toronto Stock Exchange's S&P/TSX composite index <.GSPTSE> ended down 133.58 points, or 0.93 percent, at 14,278.49. All of the index's 10 main groups fell, adding to Wednesday's bruising retreat.

"The markets have been frenetic," said Irwin Michael, portfolio manager at ABC Funds. "I think all of us, all investors, are waiting for a little bit of serenity."

He said investors remained nervous about the Chinese stock market, which snapped a five-day sell-off after heavy intervention from Beijing, and cliffhanger talks on Greece, despite little direct links to Europe for many Canadian stocks.

"However, the real effect is on investor psychology, people get nervous. More likely than not they're selling their winners," he said.

Suncor Energy Inc (>> Suncor Energy Inc.) was the biggest drag, down 1.9 percent at C$33.79, while the overall energy group fell 1.3 percent despite oil bouncing off a three-month low.

A sharp drop in oil prices and risk aversion sparked by an equities selloff in China had sent the TSX down nearly 1.5 percent on Wednesday, but moves by Beijing to stem the country's stocks rout helped calm some global markets on Thursday.

"But those issues still fester," said John Ing, president of Maison Placements Canada "We're in uncharted waters as far as the Greece exit, and the (Chinese) market collapse is only 30 percent after a 150 percent gain."

The most dramatic decliner on the index was Pacific Rubiales Energy Co (>> Pacific Rubiales Energy Corp), which plunged 39.1 percent to C$3.20 after Mexican industrial conglomerate Alfa SAB de CV (>> Alfa SAB de CV) and energy investment firm Harbour Energy Ltd dropped their plans to buy the Canadian oil and gas company.

Pacific Rubiales' shares have tumbled 75 percent over the past year on sinking crude prices and a heavy debt load.

Helping limit the damage were First Quantum Minerals Ltd (>> First Quantum Minerals Limited), up 4.6 percent to C$15.41, and Lundin Mining Corp (>> Lundin Mining Corporation), which gained 4.4 percent to C$4.95.

Declining issues outnumbered advancers by 186 to 55, for a 3.38-to-1 ratio on the downside. The index posted 1 new 52-week highs and 16 new lows.

(Additional reporting by Solarina Ho; editing by Peter Galloway and David Gregorio)

By Alastair Sharp