TORONTO (Reuters) - Toronto's main stock index tumbled hard yesterday as slowing growth in China, worry over looming euro-zone bank repayments and a drop in US consumer confidence unnerved stock markets around the world.

All 10 sectors of the index were hit, but it was weakness in the energy, financials and materials sectors - the TSX index's three main pillars - that pushed it to its lowest level since May 21.

Teck Resources plunged 5.7 percent to C$31.77 and First Quantum Minerals shed 6.4 percent to C$54.50, pushing the index's base-metal mining sector down almost seven percent as prices for Canadian commodities got caught in yesterday's downward spiral.

The index's energy sector fell 3.5 percent, dragged down by Suncor Energy , which lost 4.1 percent to C$31.65, and by Canadian Natural Resources , down 3.3 percent to C$35.05.

The index's fall was largely driven by a revision to the Conference Board's leading economic index for China to a 0.3 percent gain in April instead of the 1.7 percent rise the group had reported earlier. "People want the Chinese economy to slow down but it's a matter of how much," said Ian Nakamoto, director of research at MacDougall, MacDougall & MacTier.

Jean-Francois Dion, vice-president and portfolio adviser at RBC Dominion Securities, saw the Chinese revision as the main market-moving headline.

"Given how important China is in the current environment and how much concern there's been to the growth in China, I think that's absolutely what's moving the market today," Dion said.

The Toronto Stock Exchange's S&P/TSX composite index closed 343.17 points, or 2.96 percent, lower at 11,263.83. The day's low was 11,244.03.

Also driving the index down was data that showed US consumer confidence fell steeply in June as worries about the labour market grew.

The market was already jittery about scheduled bank repayments worth 442 billion euros to the European Central Bank tomorrow that could leave a liquidity shortfall in the financial system of more than 100 billion euros.

Financials lost 3.3 percent. Royal Bank of Canada , the country's biggest lender, was down 3.1 percent at C$51, and Bank of Montreal was 3.7 percent lower at C$57.35.