Comcast Corp (CMCSA), the largest U.S. cable operator, reported a better-than-expected quarterly profit, helped by strong growth in high-speed internet subscribers.

The company's shares rose 2 percent to $54.96 in premarket trading on Tuesday. The stock has gained 3.6 percent so far this year through Monday's close.

Net income attributable to Comcast rose to $1.99 billion, or 76 cents per share, in the second quarter ended June 30, from $1.73 billion, or 65 cents a share, a year earlier.

Excluding items, the company earned 75 cents per share, higher than the average analysts' estimate of 72 cents, according to Thomson Reuters I/B/E/S.

Revenue at Comcast's high-speed internet business rose about 10 percent in the quarter, helped by 203,000 net customer additions.

That was above the 161,000 analysts were expecting, according to market research firm StreetAccount.

The company's total revenue rose 3.5 percent to $16.84 billion, but fell short of the average analysts' expectation of $16.95 billion due to weakness in its cable business and at NBC Universal.

Comcast's cable business revenue rose only 1.2 percent to $5.18 billion. It lost 144,000 net video subscribers, more than the 123,000 analysts were expecting, according to StreetAccount.

NBC Universal revenue inched up 0.3 percent to $6.02 billion, and also fell short of analysts' expectation $6.19 billion, according to StreetAccount.

The company blamed fewer movie releases in its filmed entertainment unit for the slow growth in revenue at NBC Universal.