* Wall St ends higher as blue chips rally; Intel up late
* Bonds rise on safety buying
* Russia says Ukraine on brink of civil war
* Brent oil falls as investors weigh Libya, Ukraine (Adds close of U.S. markets)
By Herbert Lash
NEW YORK, April 15 (Reuters) - Global equity markets traded flat and government debt rose on Tuesday over rising tensions in Ukraine after Russia declared the country on the brink of civil war, though Wall Street stocks managed to end higher in a volatile session as blue chips advanced.
But weakness in many momentum names -- the technology and biotechnology shares that have been high-flyers -- limited the Nasdaq's advance.
Concerns over escalating conflict in Ukraine drove U.S. bond purchases, while data showing disappointing growth in manufacturing in New York state pointed to sluggishness in the economy and added to the bid for safe-haven bonds.
Separately, confidence among U.S. homebuilders remained downbeat, according to the NAHB/Wells Fargo Housing Market index, which rose only a point to 47 in April, the third month in a row it was below 50. Readings below 50 mean more builders view market conditions as poor than favorable.
European stocks were held back by the worries over the escalating tensions in Ukraine and weak results by bellwethers including Nestle. The FTSEurofirst 300 index of top European shares closed down 0.96 percent at 1,306.85 and kept a damper on a measure of global equity activity.
Dow components Coke and J&J rose after reporting quarterly results, while names in the Internet and biotech space fell, a sign investors were rotating from growth into value stocks. High-growth stocks have been under pressure in recent weeks after their sharp rise in prices took valuations to levels considered unsustainable.
The Nasdaq Biotech index rebounded 0.9 percent after earlier trading down more than 3.5 percent.
"The market is trying to stabilize, and investors are looking for high-quality names that have stability in their earnings and prices," said Bruce McCain, chief investment strategist at Key Private Bank in Cleveland. "This afternoon's move is part of that same flight to quality."
Russia declared Ukraine on the brink of civil war as Kiev said an "anti-terrorist operation" against pro-Moscow separatists was under way, with troops and armored personnel carriers seen near a flashpoint eastern town.
"We're cautious in the short term, we're waiting to see how the geopolitical situation evolves. There are a lot of uncertainties about Ukraine, which could become a negative catalyst for stocks if things spin out of control," said Barclays France director Franklin Pichard.
MSCI's all-country world stock index traded flat after Wall Street's close.
The Dow Jones industrial average rose 89.32 points, or 0.55 percent, to 16,262.56, the S&P 500 gained 12.37 points, or 0.68 percent, to 1,842.98, and the Nasdaq Composite added 11.467 points, or 0.29 percent, to 4,034.161.
After the closing bell, Intel Corp shares rose 3 percent to $27.56 after the chipmaker reported first-quarter results and gave an outlook.
Yahoo Inc shares jumped 8 percent in after-hours trade, to $36.90. The company reported only a slight rise in its core advertising business in the first quarter, but the shares jumped on strong results from Alibaba Group Holding Ltd, the Chinese e-commerce company in which Yahoo holds a 24 percent stake.
Over all, corporate results have been weak so far. Of the 36 companies in the S&P 500 that have reported earnings to date for the first quarter, only 52.8 percent have topped analyst expectations. In a typical quarter over the past two decades, 62 percent of companies beat estimates.
U.S. Treasuries prices gained as the rising tensions in Ukraine sparked a safety bid.
Benchmark 10-year notes were up 3/32 in price to yield 2.6301 percent.
The dollar rose slightly against the euro in late trade. The euro recovered against the dollar on Monday after the European Central Bank president, Mario Draghi, indicated over the weekend that the central bank would act to prevent deflation in the euro zone.
The dollar edged higher against the euro, up 0.04 percent at $1.3813.
The dollar was up 0.11 percent against the Japanese yen at 101.93, and was up 0.06 percent against the Swiss franc, at 0.8801 franc.
The U.S. dollar index was last up 0.08 percent.
Benchmark Brent oil rose slightly after news that Ukrainian armed forces launched military operations in the east of the country, though gains were limited by the prospect of a resumption of oil exports from Libya.
U.S. crude futures fell 30 cents to settle at $103.75. The June contract for Brent, which will become the front-month contract on Wednesday, settled 29 cents higher at $109.36 a barrel.
Reporting by Herbert Lash; Additional reporting by Jamie McGeever in London; Editing by Chizu Nomiyama and Leslie Adler