Comcast Corp , the No. 1 U.S. cable operator, reported higher quarterly profit on Thursday due to improved cost controls and a tax gain, but lost basic video subscribers amid the weak economy and competition from phone and satellite operators.

Comcast shares rose 4.8 percent in premarket trading as the company's profitability was aided by slowing growth. It spent less on new installations and equipment while selling more high-end services like HD digital video recorders to its existing customer base.

Second-quarter net profit rose to $967 million, or 33 cents a share, from $632 million, or 21 cents a share, a year earlier.

Analysts had been expecting 26 cents a share, according to Reuters Estimates.

Revenue rose 4.5 percent to $8.938 billion. Average revenue per subscriber rose 7.4 percent to $117.74.

The Philadelphia-based company lost more than 214,000 basic video subscribers during the quarter, sending its total customer base below 24 million. This was despite the fact that customer losses would have been softened by the extension of the U.S. government-mandated digital TV transition to June 12. Analysts from Collins Stewart had expected Comcast to lose 165,000 subscribers.

The results were mixed, with financials doing better than we expected but subscriber additions missing our forecasts, said Thomas Eagan, an analyst at Collins Stewart.

Stiffer competition and the weak economy meant Comcast experienced a 65 percent drop in the number of new services it sold during the period.

Cable companies like Comcast and Time Warner Cable Inc have been battling harder to win customers amid competition from satellite TV services from DirecTV Group and DISH Network and fledgling video services from phone companies AT&T Inc and Verizon Communications .

Comcast added 65,000 high-speed Internet customers during the period, less than a quarter of the number it added a year ago. It added 233,000 digital phone subscribers, less than half the number it added a year ago. It added 250,000 digital video subscribers, compared with 320,000 a year ago.

The company said it had restarted its share buyback program, which it suspended in the third quarter of 2008.

(Reporting by Yinka Adegoke; editing by John Wallace)