TORONTO (Reuters) - The Toronto Stock Exchange's main index rose for the fourth straight session yesterday as strength in commodities overpowered a steep decline in BCE Inc after the telecom giant said its leveraged buyout deal was in doubt.

The index's big energy group was up 7.9 percent as oil rose $3.67 to end at $54.44 a barrel, tracking a rally in US stocks and after China cut interest rates.

In the energy group, Canadian Natural Resources rose 12 percent to C$49.00.

Materials advanced 6.5 percent, helped higher by a rise in base metals prices as investors bet China's rate cut would help boost demand.

"China cut its interest rates today and that is felt to be good news for demand for commodities from the biggest emerging market," Gavin Graham, director of investments at BMO Asset Management.

"Looking at it, you would say it is a reflection of the return of the demand story from the emerging markets.

The S&P/TSX composite index was up 200.66 points, or 2.38 percent, at 8,643.52, with nine of its 10 main groups higher.

The index fought back from a 2.6 percent drop earlier in the day.

Shares of BCE, Canada's biggest telecom company, sank 34.2 percent to C$25.25 as a plan by Ontario Teachers' Pension Plan and private equity funds to take over the company in the world's largest leveraged buyout looked to be in jeopardy.

BCE, the most heavily-traded stock on the TSX, said that it was unlikely to close the C$34.8 billion deal after its accountants said the company that would emerge from the buyout would not pass a solvency test because of its big debt load.

The news dragged down the broader telecoms group by 10.5 percent. Telus Corp., a main BCE rival, dropped two percent to C$38.09.

Elsewhere, shares of National Bank of Canada fell 3.5 percent to C$39.04 after it became the latest bank to issue a profit warning ahead of release of its quarterly results. The financial group ended up one percent.