Cablevision Systems Corp added fewer Internet subscribers than expected and lost video subscribers in the second quarter sending its shares down as much as 12 percent in early trading on Tuesday.

Cablevision added just 5,000 Internet customers and 27,000 phone customers during the quarter.

Analysts at Citadel Securities had forecast additions 19,000 and 27,000 phone additions.

It lost 23,000 video customers as competition from Verizon Communications' FiOS TV stepped up during the period. Citadel expected Cablevision to add 3,000 subscribers.

Collins Stewart analyst Thomas Eagan described the results as the worst result we've seen out of the cable satellite sector so far in the current quarter.

The New York cable operator also posted lower-than-expected profit of 32 cents a share compared with average forecasts of 42 cents a share, according to Thomson Reuters I/B/E/S.

Revenue rose 9.1 percent to $1.69 billion.

The company also said it has completed the spin-off of its cable networks unit AMC Networks.

Shares were down $1.66 at $17.86 on the New York Stock Exchange, after touching as low as $17.24 earlier in the session.

(Reporting by Yinka Adegoke; Editing by Derek Caney)