TORONTO (Reuters) - Toronto's main stock index fell hard for a second session and hit its lowest point in five weeks yesterday, rattled by falling commodity prices and a White House plan to crack down on risk-taking by US banks.

US President Barack Obama took aim at "too big to fail" US banks with a plan that would rein in their trading activities and ability to grow.

The Obama plan sent bank shares tumbling and major equity indexes around the world fell sharply. It was the second day of big stock market falls. Markets dived on Wednesday after China announced lending restrictions that could slow world economic growth.

Toronto-Dominion Bank was the top heavyweight decliner, down 2.52 percent at C$62.25. Bank of Nova Scotia , Manulife, Bank of Montreal and Royal Bank of Canada were also among the top 10 losers in a session that saw the index's key financials group tumble 1.84 percent.

The Toronto Stock Exchange's S&P/TSX composite index lost 210.22 points, or 1.8 percent, to close at 11,469.1, not far off its 11,461.25 low for the day.

"It's fairly a one-way street today," said Francis Campeau, broker at MF Global Canada in Montreal. "There's a bit of a Chinese hangover and Mr. Obama put the final nail in the coffin."

Resource issues were hit heavily as gold prices fell below $1,100 an ounce, their lowest level this year, and oil dropped to a 2010 low around $76 a barrel.

The index's materials group, home to gold producers, was off 3.8 percent. The oil and gas sector was down 1.7 percent.

All 10 of the TSX's main sectors were lower.

The Canadian dollar ended at C$1.0514 to the US dollar, or 95.11 US cents, down from Wednesday's finish of C$1.0470 to the US dollar, or 95.51 US cents.

The currency hit a low of C$1.0525, or 95.01 US cents, during the session, hurt by broad US dollar strength.