By Anora Mahmudova, MarketWatch

NEW YORK (MarketWatch) -- The U.S. stock market closed higher Tuesday, with the S&P 500 extending its winning streak to six days, the longest streak of gains since September 2013.

Investors welcomed better-than-expected results from Comcast Corp. (CMCSA) and Harley-Davidson, Inc.(HOG), while a flurry of deal news in the health-care sector added to positive sentiment.

The S&P 500 (SPX) ended the day 7.66 points, or 0.4%, higher at 1,879.55, rising for six straight sessions. The health-care sector lead gains thanks to deal activity between several pharmaceutical companies, including Allergan and Valeant.

The Dow Jones Industrial Average (DJI) closed off session highs, but still gained 65.12 points, or 0.4%, to 16,514.37. The Dow Transportation Index (DJT) closed at a record level after adding 48.71 points, or 0.6%, to 7,734.90.

The Nasdaq Composite (RIXF) added 39.91 points, or 1%, to 4,161.46, recording the sixth consecutive session of gains, helped by a 6% rally in Netflix, Inc. Biotechnology and pharmaceutical companies also jumped. Both the Nasdaq Biotechnology index (NBI) and the iShares Nasdaq Biotechnology ETF (IBB) rose 3.2%.

The day also continued a positive streak for Tuesday's. Tuesday is the only weekday that has averaged with a gain so far this year for the S&P 500 and the Dow, according to FactSet. Since the beginning of the year, the S&P 500 and the Nasdaq Composite fell only twice on a Tuesday. All three main indexes rose for the past six Tuesdays.

Read the recap of the MarketWatch's live blog of today's stock-market action.

Comcast, Lockheed Martin beat expectations; Allergan jumps

The day's economic data provided a little support. The sales pace of existing homes ticked down in March to the slowest rate since July 2012, according to data released Tuesday, however the decline was smaller than the consensus rate forecast by economists polled by MarketWatch. The SPDR S&P Homebuilder ETF (XHB) gained 1%.

In earnings news, Comcast Corp. (CMCSA) shares climbed 1.9% after the telecommunications company reported first-quarter earnings and revenue ahead of analyst forecasts.

"Earnings have not been stellar, especially on the revenue side, but it seems that results are good enough for investors who are in a 'buy the dip' state of mind," said Channing Smith, managing director at Capital Advisors.

"Deals are helping markets, but it is a worrying sign when both acquisition target and acquiring companies rise after announcing a deal," he added.

Lockheed Martin Corp. (LMT) fell 3% despite the aerospace and defense firm posting better-than-expected first-quarter profit and raising its 2014 earnings guidance.

Harley-Davidson Inc. rose 6.4% after beating quarterly earnings estimates. The Milwaukee-based maker of motorcycles reported a 19% rise in first-quarter profit, despite an uptick in loan losses at the company's financing unit.

Netflix, Inc (NFLX) shares rallied 7% after the video-streaming company beat expectations for the first-quarter results.

McDonald's Corp. (MCD) shares were down 0.7% even as the company's first-quarter results missed expectations. Earnings for the first three months of the year fell, dragged by a decline in sales in the U.S. amid fierce competition and consumers' growing appetite for healthier foods.

Xerox Corp. (XRX) shares were up 1.1% after the company reported a fall in the first-quarter earnings as revenues continued to shrink. The company trimmed its full-year adjusted earnings expectations.

In deal news, shares of Allergan Inc. (AGN) surged 15% after Valeant Pharmaceuticals International Inc. (VRX) and activist investor Bill Ackman joined forces and proposed a buyout of Allergan. Valeant shares rose 7.5%.

Reporting after the closing bell, shares in AT&T (T) slid 1.4% in aftermarket action after the company's first-quarter earnings were in line with estimates.

Intuitive Surgical Inc shares drop 4% in aftermarket trade after the company fell short of Wall Street's expectations on sales and earnings for the first quarter.

In other financial markets, European stock indexes posted solid gains on their first trading day after the Easter break amid increasing deal activity in the pharma sector. Asian bourses closed mixed. Meanwhile, oil declined and most metals prices moved higher.

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