Marlboro maker Altria Group said Thursday that it will cut the number of salaried workers at its cigarette business and related service subsidiaries by 15 percent as sales continue to decline industrywide.

Altria, based in Richmond, would not say how many people would be affected by the layoffs. It said that employees who will lose their jobs will be informed by mid-December and that most will leave by late February. The reductions announced Thursday do not include hourly manufacturing workers.

Altria has 10,000 employees across the United States, including about 4,600 in Virginia. Cigarettes make up the bulk of its business.

Altria announced plans to trim $400 million in annualized costs by the end of 2013, which would include about $300 million in employee separation costs and additional reductions in spending. The number of cigarettes that Altria sold declined 9 percent in the third quarter, to 33.3 billion, compared with a year ago.