Australia shares post biggest gain in a year on upbeat Fed

* Fed gives surprise upbeat assessment

* Oil bounce sends energy stocks higher

* Shares (Berlin: DI6.BE - news) bounces in relief rally (Adds analysis, quotes, stocks on the move)

SYDNEY/WELLINGTON, Dec 18 (Reuters) - Australian shares posted their biggest gain in a year on Thursday, as an upbeat economic assessment from the Federal Reserve triggered a relief-rally in global markets unnerved by financial turmoil in Russia and tumbling oil prices.

Overnight, the Fed gave a confident assessment on the economy and promised to be patient in removing policy stimulus.

A sharp bounce in oil prices off multi-year lows also provided relief for Australia's battered energy sector.

"The rally was inspired by the FOMC statement last night," said Ben Le Brun, a market analyst at OptionsXpress, referring to the Fed's Federal Open Market Committee.

"The other factor is the (upward) pressure in the oil market and commodities that will feed through the performance of the Aussie stock market."

The S&P/ASX 200 index surged 1.6 percent or 83.44 points to 5245.3 by 0120 GMT, its biggest one-day rally since Dec. 19, 2013, and closing on its highest intraday level in a week.

QBE Insurance Group, which has significant business in the U.S., led the financial sector higher, rallying 4.8 percent. Australia and New Zealand Banking Group and National Australia Bank each rose 1.6 percent.

Among large miners, BHP Billiton (NYSE: BBL - news) rose 2.7 percent and Rio Tinto (Xetra: 855018 - news) added 2.9 percent, while gold major Newcrest Mining surged 4 percent and iron ore producer Fortescue Metals Group surged 6.4 percent.

Energy stocks followed oil's bounce: Woodside Petroleum (Other OTC: WOPEF - news) added 2.6 percent and Santos rallied 6.3 percent.

Elsewhere, fund manager Challenger Ltd bounced 7.4 percent after it said it resolved a long-running court action.

Travel agent Flight Centre (Other OTC: FGETF - news) plummeted 9 percent after issuing a profit downgrade and travel insurer Cover-More fell 7 percent because of concerns about domestic travel growth.

New Zealand's benchmark NZX50 index rose 23.1 points or 0.4 percent to 5,519.73 in early trade, tracking gains in Asian markets and hovering near a record closing high of 5,542.93.

Gains were limited as investors were cautious amid the recent global market volatility.

Pacific Edge jumped 3.7 percent to NZ$0.85, recovering from a three-week low of NZ$0.820 after the cancer testing company reported a surge in half-year revenues as it expands further into the U.S. market.

Spark rose 0.8 percent after the country's dominant telecommunications company said it was partnering with Vodafone and Australia's Telstra to build a trans-Tasman submarine cable to bolster broadband traffic. (Reporting Byron Kaye, Cecile Lefort and Naomi Tajitsu; Editing by Shri Navaratnam)