SAN FRANCISCO — Apple Inc. said Monday that it sold 9 million units of its top-of-the-line iPhone 5S and less-expensive iPhone 5C during their first three days on sale.

That trounced the performance of last year's model, the iPhone 5, which sold 5 million units in its opening weekend.

The iPhone 5S and 5C's quick start also surpassed analyst forecasts that predicted Apple would sell somewhere from 6 million to 8 million models during the first weekend.