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By Brad Dorfman

CHICAGO (Reuters) - Altria Group Inc (MO.N: Quote, Profile, Research) posted lower quarterly profit from continuing operations on Thursday due to charges related to the spinoff of its Philip Morris International (PM.N: Quote, Profile, Research) business.

But earnings were in line with analysts' estimates, and the company also stood by its full-year profit forecast. The company's top-selling Marlboro cigarettes gained market share.

Altria, the parent of Philip Morris USA, said profit from continuing operations dropped to $614 million, or 29 cents a share, in the first quarter, from $696 million, or 33 cents a share, a year earlier.

Excluding charges related to the spinoff and a gain from the sale of Altria's Manhattan headquarters, earnings were 37 cents a share, matching the average analyst estimate compiled by Reuters Estimates.

Revenue excluding excise tax was $3.6 billion, in line with analysts' estimates and up slightly from a year earlier. The company shipped 40.1 billion cigarettes, down 1.2 percent from a year earlier.

U.S. cigarette consumption has fallen steadily since 1981 as more bans have been enacted and health messages become more prevalent.

Soaring government taxes on cigarettes are also testing the notion that cigarette demand is not affected much by higher prices.