US STOCKS-Wall St slumps, Nasdaq under 50-day moving average

* Ukraine conflict continues, Russia seizes marine base

* Weak China data raises hopes for stimulus

* Nasdaq hit as trading favorites like Netflix (NasdaqGS: NFLX - news) , Tesla sink

* Herbalife (NYSE: HLF - news) rallies; Icahn to get more reps on board

* Indexes down: Dow 0.3 pct, S&P 0.7 pct, Nasdaq 1.5 pct (Updates prices)

By Ryan Vlastelica

NEW YORK (Frankfurt: HX6.F - news) , March 24 (Reuters) - U.S. stocks fell sharply on Monday, with the Nasdaq suffering its biggest daily percentage decline since early February, as the ongoing crisis in Ukraine pushed investors to take profits in some of the market's biggest trading favorites.

The Nasdaq's losses took it below its 50-day moving average, a sign of weakening near-term momentum, and almost 80 percent of issues traded on the exchange were lower. About two-thirds of New York Stock Exchange-listed shares were lower, and eight of the ten S&P 500 sectors dropped on the day.

Futures had been higher throughout the premarket session, lifted by hopes that China would take stimulative measures to support its economy, but indexes turned lower early, with the Nasdaq especially hit hard by steep losses in some of its biggest recent outperformers. Netflix Inc dropped 6.7 percent to $378.60, Tesla Motors (Xetra: A1CX3T - news) shed 5.5 percent to $216.35 and Facebook Inc (NasdaqGS: FB - news) slid 4.4 percent to $64.25.

Netflix was the S&P's biggest percentage gainer in 2013, while Tesla soared 344 percent last year and extended that rally by more than 40 percent so far this year.

"If we went into an extended period of profit-taking, [these stocks are] where a significant amount of the profits are, and that's where a significant amount would be taken," said Art Hogan, chief market strategist at Wunderlich Securities in New York.

Ukraine announced the evacuation of its troops from Crimea, essentially yielding the region to Russian forces, which seized a Ukrainian marine base. While few U.S. companies have excessive exposure to the region, investors are concerned about the potential economic fallout from any escalation in tensions.

U.S. President Barack Obama, who has imposed personal sanctions against some of Russian President Vladimir Putin's political and business allies, began crisis talks with his European allies over how to respond in the biggest East-West conflict since the Cold War.

"The issue remains contained for the time being, but Obama will try and garner support for more sanctions, which will ultimately shape our view of how things can end up looking," Hogan said. "This remains at the forefront of what we're paying attention to."

The Dow Jones industrial average was down 54.58 points, or 0.33 percent, at 16,248.19. The Standard & Poor's 500 Index was down 12.56 points, or 0.67 percent, at 1,853.96. The Nasdaq Composite Index was down 65.13 points, or 1.52 percent, at 4,211.66.

Losses were limited in the Dow by a rise in Procter & Gamble Co, a consumer staple that is considered a defensive play. That stock rose 2.2 percent to $79.56, snapping a four-day losing streak.

China's manufacturing engine contracted in the first quarter of 2014, according to the flash Markit/HSBC Purchasing Managers' Index. The report came in below expectations but raised hopes for new stimulative measures.

In the latest U.S. economic data, financial data firm Markit said its preliminary read on March manufacturing activity slowed after nearing a four-year high last month, but the rate of growth and the pace of hiring remained strong.

Herbalife Ltd said it would allow three more representatives of billionaire investor Carl Icahn, the company's biggest shareholder, to join its board. Shares of the nutrition and weight-loss company jumped 6.5 percent to $52.77.

NU Skin Enterprises Inc (NYSE: NUS - news) shares soared 19 percent to $89.52 on heavy volume. Earlier, China fined the company more than $500,000 for illegal product sales and misleading local consumers, China's State Administration for Industry & Commerce said in a statement on its website. NU Skin last week said it expected a fine.

The Wall Street Journal reported that Apple Inc (NasdaqGS: AAPL - news) was in talks with Comcast Corp to enter a deal for a streaming-television service that would allow Apple set-top boxes to bypass congestion on the web. The companies declined to comment on the report. Shares of Apple rose 0.8 percent to $537.32 while Comcast dipped 0.8 percent to $49.59. (Editing by Bernadette Baum and Nick Zieminski)