TORONTO (Reuters) - Toronto's main stock index surged more than five percent yesterday to its highest close in six weeks as a massive takeover of Petro-Canada and a US plan to rid banks of toxic assets helped boost sentiment.

Energy shares raced higher as the price of oil, a key Canadian commodity, hit a three-month high, while Suncor Energy Inc. agreed to buy rival Petro-Canada for C$18.43 billion.

Shares of Petro-Canada, a key contributor to the Toronto market's gain, soared 20.4 percent to C$35.70, while EnCana Corp jumped eight percent to C$55.50.

Another key factor behind the gains was the US plan to buy up to $1 trillion in toxic financial assets, a move that will be critical to hopes for a US economic recovery.

"This is the most credible plan I've seen from the US Treasury to date and it looks like the private sector and the stock market is buying into it," said Ian Nakamoto, director of research at MacDougall, MacDougall & MacTier. "For me, this is some validation that there is some meat on the bones here."

The Toronto Stock Exchange's S&P/TSX composite index rose 452.16 points, or 5.32 percent, to close at a session high of 8,958.51.

All 10 of the TSX's sectors ended comfortably higher.

The financials index led with a 8.9 percent gain, while the energy group followed with a rise of 7.4 percent.

Shares of Canadian banks and insurers followed their US counterparts higher as the US bailout plan helped boost optimism about a revival in US bank lending, and the sentiment spilled over to Canada.

Royal Bank of Canada, the main driver of the TSX's gain, rose 7.6 percent to C$37.94, while shares of insurer Manulife Financial posted a 15.8 percent rise to C$16.26.

The broad-based rally extends a torrid stretch of gains by the TSX, which has closed higher in nine of its past 10 sessions. The index is now nearly 20 percent above the five-year lows it saw earlier this month.

Capping yesterday's rally was weakness in some key gold-mining stocks, which fell alongside the price of bullion as optimistic investors stepped away from safe haven investments such as gold.

Barrick Gold Corp. shares dropped two percent to C$40.54, while Goldcorp slid one percent to C$41.82.