REFILE-UPDATE 1-Blockbuster posts lower-than-expected revenue

(Refiles to fix typo in third paragraph)

* Blockbuster posts Q2 loss of 21 cents

* Same-store sales fall 17.8 percent

* Shares fall 21 percent

LOS ANGELES, Aug 13 (Reuters) - Blockbuster Inc (BBI.N) on Thursday posted lower-than-expected quarterly revenues and same-store sales, citing stiff competition in the DVD rental market, and its shares fell 21 percent.

The company reported a net loss for the second quarter that narrowed to $39.7 million, or 21 cents per share, from a net loss of $44.7 million, or 23 cents per share a year earlier.

But revenues slid to $1.02 billion from $1.3 billion as same-store sales fell 17.8 percent.

Analysts on average had been expecting revenues of $1.1 billion for the quarter, according to Reuters Estimates.

Michael Pachter, of Wedbush Morgan Securities, said he had forecast same-store sales to fall 8.5 percent in the quarter.

Shares in Blockbuster fell 21 percent to 68 cents in after-hours trade, versus a close of 86 cents. (Editing by Carol Bishopric)