TREASURIES-Prices up on quarter-end buying by institutions

* Gains biggest in long maturities

* Treasuries on track for fifth straight up quarter (Adds late prices, quarterly performance data)

By Michael Connor

NEW YORK, March 31 (Reuters) - U.S. Treasury debt prices rose on Tuesday on buying by institutional investors preparing their portfolios for the end of the quarter, a period in which prices of government securities rose.

Prices were up in most maturities, with the largest gains in long-dated issues, and were keeping Treasuries on track for a fifth straight quarter of gains.

The benchmark 10-year Treasury note was yielding 1.9353 percent, reflecting a price rise of 8/32, according to Thomson Reuters data.

Buyers included institutions aligning holdings with portfolios based on indexes and other benchmarks and U.S. banks needing to match stricter liquidity coverage ratios that came into effect this year, according to rates strategists.

"We are also getting a little bit of safe-haven buying on the margin," said Guy LeBas, chief fixed-income strategist at Janney Montgomery Scott in Philadelphia.

Anxieties in Europe over Greece's finances were keeping the euro on track for its biggest losing quarter since the currency's introduction as central bankers in the region buy bonds in order to depress interest rates and boost business conditions.

Uncertainty over the talks in Switzerland on hammering out a nuclear deal between Iran and global powers was also driving some bids for Treasuries, according to Vishal Khanduja, portfolio manager for Calvert Investments.

Wall Street, which rallied on Monday as bonds softened, was down on Tuesday.

The 30-year Treasury bond was last up 8/32 in price and yielding 2.5389 percent, while the five-year note was ahead 6/32 and yielding 1.3815 percent.

Treasuries, which carry substantially higher interest rates than comparable government securities around the world, are on track for a winning first quarter even as the Federal Reserve comes closer to raising interest rates for the first time since 2006.

The first three months of 2015 should mark a fifth straight quarter of gains for Treasuries, according to Bank of America (Swiss: BAC.SW - news) Merrill Lynch's U.S. Treasury Index. Through Monday, the index had total returns of 1.587 percent for the quarter.

"We are still in the environment where our central bank is leaning dovish," said Boris Rjavinski, strategist at UBS (NYSEArca: FBGX - news) in Stamford, Connecticut. "Until we see a palpable change there, it's not surprising that investors are comfortable holding Treasuries."

Treasuries narrowed price gains after the release of the S&P/Case Shiller composite index, which showed that housing prices in 20 U.S. metropolitan areas gained 4.6 percent in January over the year-earlier month. That outpaced December's downwardly revised gain of 4.4 percent. (Reporting by Michael Connor in New York; Editing by Leslie Adler and Chizu Nomiyama)