MELBOURNE, Sept 19 (Reuters) - Australian shares extended gains to 4.5 percent on Friday, boosted by strong buying in banking shares on hopes that efforts to sequester Wall Street's bad debts will help the financial sector recover. Investment bank Macquarie Group Ltd surged 50 percent to A$39.10 after plunging in recent days on concerns about its ability to fund its business model. Central banks around the world pumped billions of dollars into credit markets and U.S. authorities shopped a plan to mop up bad loans [nHKG93628] after previous actions including massive bailouts had failed to restore market confidence. The benchmark S&P/ASX 200 index <.AXJO> rose 208.3 points to 4,815.6, the biggest one-day gain since Jan. 25, 2008, after closing on Thursday a near three-year closing low. It had lost 6 percent over the first four days of this week. New Zealand's NZX-50 index <.NZ50> was up 1.8 percent at 3,216.1.
