Sinclair Broadcast Group Inc. said yesterday that its third-quarter loss narrowed as advertising sales continued to increase.

The Hunt Valley-based broadcaster posted a net loss of $21.4 million, or 28 cents a share, for the three months that ended Sept. 30. That compared with a loss of $29.9 million, or 39 cents a share, a year earlier.

Net broadcast revenue was $163.9 million, up from $148.6 million. Local third-quarter advertising revenue was 10.7 percent higher than in last year's corresponding period. National advertising rose 12.2 percent.

"Third-quarter results continued to reflect an improving advertising market, with strength coming from many segments of the business," said David Smith, Sinclair president and chief executive officer.

Sales were particularly strong in the automotive, services, home products, telecommunication and medical sectors. A strong election season also helped to boost revenue, but Sinclair officials said the company performed well excluding political advertising.

Broadcast cash flow, a key benchmark of performance, increased 24.2 percent, to $71.3 million from $57.4 million a year earlier.

Sinclair officials predicted that advertising sales will continue to improve through the fourth quarter.

Sinclair, which owns or operates 62 television stations, also announced yesterday that it had begun a local news network to be used in markets that typically can't normally support traditional news programs. It was started in the Flint-Saginaw-Bay City, Mich., market.

Sinclair stock closed yesterday at $12.37, up $1.53.