The Toronto Stock Exchange's S&P/TSX composite index <.GSPTSE> fell 86.14 points, or 0.55 percent, to close at 15,543.33. Seven of the index's 10 key sectors lost ground.

Financial stocks, which account for roughly a third of the index's weight, slipped 0.7 percent, as Toronto Dominion Bank (>> Toronto-Dominion Bank) fell 0.9 percent to C$63.13, leading the group's declines.

John Ing, president of Maison Placements Canada, said market gyrations will continue given the concerns about the banks' exposure to Canada's overheated housing market.

"Home Capital is still in intensive care. Until that and other evidence of the housing market settles down - then I think people will stop focusing on the bank," he said.

Home Capital Group Inc (>> Home Capital Group Inc) has struggled with financing problems following accusations by the Ontario Securities Commission that it made misleading statements to investors.

Oil and gas companies retreated in tandem with the price of crude, which fell ahead of weekly U.S. inventory data. U.S. crude prices were down 1.3 percent to $48.23 a barrel.

The overall energy group dropped 1.3 percent, with Enbridge Inc (>> Enbridge Inc) down 1.3 percent to C$53.84.

Loyalty program provider Aimia Inc slumped 11.7 percent to C$3.18. Its shares have been battered after Air Canada (>> Air Canada) announced last week that it would start its own loyalty program in 2020.

Air Canada stock touched its highest level since November 2007 and closed up 5 percent at C$16.95 after the Canadian government unveiled new rules that could help carriers form joint ventures and attract foreign investment.

The materials group, home to natural resource companies, was among the few other bright spots in the market, rising 0.7 percent, helped in part by higher gold prices. Franco Nevada Corp (>> Franco Nevada Corp) rose 1.9 percent C$99.50, while Wheaton Precious Metal Corp , formerly known as Silver Wheaton Corp, rose 2.6 percent C$29.26.

BlackBerry Ltd (>> BlackBerry Ltd) shares closed up 5.3 percent at C$13.84, after touching their highest level since March 2015 during intraday trading. One analyst said the company was working with automakers on an anti-hacking tool, while another said it was benefiting from interest in cyber security-related stocks following the WannaCry ransomware attack. [L2N1II1LK]

Declining issues outnumbered advancing ones on the TSX by 147 to 99, for a 1.48-to-1 ratio on the downside.

The index was posting 18 new 52-week highs.

(Reporting by Solarina Ho; Editing by Bill Trott)

By Solarina Ho