* Bonds rise on safety buying
* Russia says Ukraine on brink of civil war
* Brent oil falls as investors weigh Libya, Ukraine (Adds opening of U.S. markets, byline; dateline previously LONDON)
By Herbert Lash
NEW YORK, April 15 (Reuters) - Global equity markets declined and government debt rose on Tuesday as tensions spiked in Ukraine as Russia declared the country on the brink of civil war and as disappointing corporate results dogged U.S. and European stock markets.
The New York Federal Reserve said its Empire State general business conditions index fell to a five-month low of 1.29 in April from a reading of 5.61 the month before, pulled down by a plunge in new orders.
A separate report showed confidence among U.S. homebuilders remained downbeat as the NAHB/Wells Fargo Housing Market index 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.
Worries over escalating tension in Ukraine and weak results by bellwethers including Nestle held back stocks in Europe. Wall Street fell as Nasdaq slumped on another round of selling in technology and biotech names.
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 fell 0.5 percent, while the FTSEurofirst 300 index of top European shares was down 0.91 percent at 1,307.43.
The Dow Jones industrial average fell 30.38 points, or 0.19 percent, to 16,142.86. The S&P 500 lost 3.84 points, or 0.21 percent, to 1,826.77 and the Nasdaq Composite dropped 35.19 points, or 0.87 percent, to 3,987.505.
Results also weighed on U.S. stocks. Of the 36 companies in the S&P 500 that have reported earnings to date for the first quarter, 52.8 percent have reported earnings above 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 for U.S. bonds. The weak New York state manufacturing survey and housing data pointed to sluggish economic momentum.
Benchmark 10-year notes were up 4/32 in price to yield 2.6229 percent.
The dollar pared gains against the euro after traders discounted comments from European Central Bank policy-makers and a slight uptick in U.S. inflation did not suggest a potential change in the Federal Reserve's dovish monetary stance.
The euro recovered against the dollar after ECB President Mario Draghi indicated on Saturday that the central bank would act to prevent deflation in the euro zone.
The impact of Draghi's comments receded somewhat, with traders awaiting more decisive action from the ECB.
The dollar edged up against the euro, trading up 0.05 percent against the dollar at $1.3811.
The dollar was down 0.22 percent against the Japanese yen at 101.62, and was down 0.11 percent against the Swiss franc to trade at 0.8789 francs.
The U.S. dollar index was last up 0.07 percent.
Brent crude fell further below $109 as investors weighed the prospect of a gradual recovery in Libyan oil exports against rising tension between Russia and Ukraine.
Brent shed 27 cents to $108.80 a barrel. U.S. oil dropped 17 cents to $103.88 a barrel.
(Additional reporting by Jamie McGeever in London, reporting by Herbert Lash)