Allianz Life Insurance of North America on Tuesday posted a 72 percent increase in first-quarter operating profit of $217 million compared with $126 million last year.

Marc Olson, vice president of finance, said the improved earnings were driven by gains on the sale of appreciated bonds and an 11 percent growth in assets under management to $98.5 billion.

The company said premium revenue was flat at $2.7 billion.

Fixed-annuity premiums of $1.5 billion were down 6 percent from the first quarter of 2011. Variable-annuity sales were up 8 percent to $1 billion. Life insurance sales nearly tripled to $17 million.

Golden Valley-based Allianz Life North America, which employs about 1,700, is part of Germany's huge Allianz SE; it sells annuities whose returns are tied to stock market indexes and other retirement and insurance products through an independent sales force.

Allianz SE's North American holdings also include Fireman's Fund Insurance Co. and asset management business PIMCO.

NEAL ST. ANTHONY