*U.S.-Russia tension drives oil price higher
*Materials shares up as metal prices rise
*Nortel buys online voice technology firm
TORONTO, Aug 21 (Reuters) - The Toronto Stock Exchange's main index was sharply higher at midday on Thursday as energy and materials shares climbed with commodities prices.
The S&P/TSX composite index .GSPTSE was up 188.93 points, or 1.4 percent, at 13,539.06, with seven of its 10 main groups higher. On Wednesday, the index gained 2 percent, helped by a surge in resource stocks.
The heavyweight energy and materials groups again led the way up on Thursday, rising 2.4 percent and 3.9 percent respectively. In the oil patch, Husky Energy (HSE.TO) rose 4.6 percent to C$48.90.
U.S. oil edged above $120 a barrel, up for a third straight session, as Washington's missile shield deal with Poland angered Russia, heightening tension. See [ID:nSP213151]
The gold price rose above $830 an ounce as the U.S. dollar weakened, while base metals prices were also higher.
Elsewhere, Nortel Networks Corp NT.TO NT.N slipped 0.3 percent to C$6.31. It said on Thursday it is buying DiamondWare, a company that provides voice communications for online game platforms and virtual worlds.
Rogers Communications (RCIb.TO) rose 3.4 percent to C$37.36. The telecom firm, the owner of Canada's biggest wireless carrier, began offering Research In Motion Ltd's RIM.TO new BlackBerry Bold in Canada on Thursday. RIM slipped 0.5 percent to C$137.68.
Maple Leaf Foods Inc (MFI.TO) shares fell 4.2 percent to C$10.15 after the company announced on Wednesday a recall of packaged deli meats and temporarily closed the Toronto plant where they were made after some were found contaminated with listeria bacteria. [ID:nN20472780] ($1=$1.05 Canadian) (Reporting by Jennifer Kwan; Editing by Peter Galloway)