* Stocks up, govt bonds down on US rescue of mortgage giants
* Yen suffers as risks reduced by prop to US housing market
* Global financial crisis still wears on, analysts say (Updates prices, adds quote)
By Kevin Plumberg
HONG KONG, Sept 8 (Reuters) - Asian stocks surged 4 percent and government bonds tumbled on Monday after Washington took over Fannie Mae and Freddie Mac to save the U.S. housing market and limit the extensive damage of the financial crisis.
Investors, who have been keeping their portfolios heavy with cash, devoured bank shares and ploughed into most Asia-Pacific currencies as the rescue of the top mortgage finance companies, possibly the biggest U.S. government bailout ever, helped willingness to take risks.
Still, the impact of the rescue package on the U.S. government's fiscal position could ultimately hurt the U.S. dollar, some analysts said, a prospect that helped to send Treasury yields higher.
"You do take some of default risk out of the market, so in that sense this is good for other financial assets. You have reduced systemic default risk," said Paul Schulte, regional strategist with Lehman Brothers in Hong Kong.
"Longer-term we have a lot more glass to crawl over because we have arrangements with other financial institutions that need to get worked out," he said.
Japan's Nikkei share average <
> rose 3.6 percent, bouncing from a 5-1/2-month low on Friday.Stocks of large banks such as Mitsubishi UFJ Financial Group <8306.T> and Mizuho Financial Group <8411.T> rallied 12.3 percent and 11.4 percent, respectively.
The MSCI index of Asia-Pacific stocks traded outside of Japan <.MIAPJ0000PUS> was up 4.4 percent, rebounding from the lowest since October 2006. It was on track for the biggest daily gain since January 2008.
Hong Kong's Hang Seng index <
> was up 3.9 percent, led by shares of Europe's largest lender HSBC Holdings <0005.HK>.BUYING BACK RISK
Dealers in the currency market scrambled to sell yen for just about every major currency after last week knocking down the euro to the lowest in a year against the yen because of fears the global economy was slowing rapidly.
The euro jumped to 156.35 yen <EURJPY=R>, up 1.8 percent from late in New York on Friday and shot as high as 156.93 yen on trading platform EBS. The dollar climbed 0.7 percent to 108.55 yen <JPY=> and was as high as 109.05 earlier in the morning.
The U.S. currency fell 1.4 percent against the Singapore dollar <SGD=> and 1.6 percent against the Malaysian ringgit <MYR=>.
The U.S. government on Sunday seized control of mortgage finance companies Fannie Mae <FNM.N> and Freddie Mac <FRE.N>, which own or guarantee half of all U.S. mortgages, ending weeks of speculation after regulators judged the companies' shrinking capital position left them too vulnerable. [
]As part of the plan, the Treasury is taking an equity stake in the companies and promised to purchase mortgage-backed securities they issue and provide however much liquidity is necessary to keep them afloat -- actions that together could top $200 billion.
Asian local currency debt yields narrowed relative to their benchmarks and credit default swap spreads were also expected to tighten as investors repriced the level of risk in markets.
"By removing a nearly $5 trillion uncertainty over agency debt from the market, we anticipate a snap rally in credit this morning. Asian sovereigns notably Korea should be principal beneficiaries of the U.S. governments credit backstop in that debt class," said Brett Williams, credit analyst with BNP Paribas, in an email to clients.
However, Citigroup analysts said the longer Washington increases its debt by figuring a way out essentially to restructure the housing market, the more the dollar and U.S. assets in general are seen in a negative light.
"This stops well short of the 'nightmare scenario' where foreign investors start to sell the stock of their U.S. holdings, triggering a U.S. dollar collapse, but represents another factor arguing against more dollar-favorable capital flows," the analysts said in a note.
U.S. Treasuries fell sharply in reaction to the Fannie and Freddie bailout. Benchmark 10-year Treasury prices fell, pushing up yields to 3.80 percent <US10YT=RR>, up from 3.71 percent in late U.S. trading on Friday.
Japanese government bond futures fell, following a slide in U.S. Treasuries and a surge in equity markets. September 10-year futures <2JGBv1> slumped 1.32 points to 137.36 after rising to a five-month peak of 139.09 on Friday.
Oil prices rose more than $2 a barrel, supported by worries Hurricane Ike would tear through the Gulf of Mexico and further crimp rig activity in what has been a busy storm season. U.S. light crude for October delivery <CLc1> was at $108.51 a barrel. (Editing by Jean Yoon)