* Ex-Japan Asia MSCI down 0.5 pct, Nikkei loses 0.5 pct
* Bitcoin skids as S Korea prepares bill to ban cryptocurrency trade
TOKYO, Jan 11 (Reuters) - The New Year rally in Asian shares petered out on Thursday due to concerns about rising U.S. protectionism, while bond markets nursed steep losses and Bitcoin fell more than 11 percent after moves in South Korea to ban trade in the cryptocurrency.
MSCI's broadest index of Asia-Pacific shares outside Japan shed 0.5 percent, slipping further from Tuesday's 10-year peak. Japan's Nikkei also lost 0.5 percent.
Bitcoin dropped to $13,189 on the Bitstamp exchange, after South Korea's justice minister said a bill was being prepared to ban cryptocurrency trading.
Bond markets were spooked by the Bank of Japan's routine announcement on Tuesday of a reduction in purchases of longer-tenor bonds, as well as reports that China is reducing its U.S. Treasuries purchases and a jump in oil prices.
Those factors combined to push 10-year Treasury yields to their highest levels since March, and also pressured the dollar and stock markets.
But the media reports on China considering reducing or halting purchases of U.S. Treasuries could be based on wrong information, a Chinese government source said on Thursday.
U.S Treasuries pared some of their losses on Thursday. The 10-year yield stood at 2.536 percent in Asian trade, below their U.S. close on Wednesday of 2.549 percent.
"That should have been good news for the U.S. dollar, but it's still trading very weakly - it's a weak dollar story," said Masashi Murata, currency strategist for Brown Brothers Harriman in Tokyo. "The market seems to have been looking for one-sided news to sell the dollar, this week."
U.S. shares snapped their New Year rally on Wednesday while the Canadian dollar and the Mexican peso fell after a Reuters report said Canada increasingly believes that U.S. President Donald Trump will soon announce his intention to withdraw from the North American Free Trade Agreement treaty.
U.S. bond prices tumbled, boosting the benchmark 10-year Treasuries yield to a 10-month high of 2.597 percent after Bloomberg reported that China, the biggest foreign holder of U.S. Treasuries, could slow or stop buying government bonds.
"I would think that China is flexing its muscles as the United States is looking into measures to deal with its trade deficit with China," said Daisuke Uno, chief strategist at Sumitomo Mitsui Bank.
"I have been expecting rising trade frictions between the United States and China this year. It appears China is quick to touch the Achilles heel of the States," he added.
Reports on investigations into U.S. imports are due to be sent to Trump this month, including probes into whether imports of steel and aluminium threaten U.S. national security.
A separate probe into Chinese intellectual property practices may also conclude as early as this month, Axios reported, and could result in tariffs on the country's consumer-electronics exports.
The speculation that China may reduce its buying in U.S. bonds helped to underpin the euro, the most obvious alternative assets to the dollar.
The euro traded at $1.1948, nearly flat on the day, and holding above Tuesday's low of $1.1916.
Against the yen, the dollar added 0.3 percent to 111.76, after hitting a six-week low of 111.27 yen in the previous session when it skidded 1.1 percent to mark its largest decline in almost eight months.
The yen was buoyed this week after a cut in the Bank of Japan's bond buying on Tuesday fuelled speculation that the central bank could eventually seek to exit from its stimulus later this year, following in the footsteps of other major central banks.
The BOJ maintained the amount of its bond purchases on Thursday, helping to soothe a market rattled by its reduction earlier this week.
The Canadian dollar traded at C$1.2550 per U.S. dollar after having lost 0.7 percent on Wednesday.
Crude oil prices jumped on Wednesday and settled near three-year highs after U.S. government data showed a drop in crude inventories and production, though the fall in the latter could be the result of extreme cold temperatures across the United States.
U.S. West Texas Intermediate (WTI) crude futures traded at $63.50 per barrel, after hitting a high of $63.67 in the previous session, their loftiest level since December 2014.
Brent crude futures traded at $69.10 a barrel after rising as high as $69.37 on Wednesday, highest since May 2015.
Spot gold was up 0.2 percent at $1,319.17 an ounce after spiking to nearly four-month highs in the previous session, in line with the dollar's plunge.
(Editing by Simon Cameron-Moore)