Nokia Corp. expanded its leadership position in the mobile handset market in 2006, shipping more units than its next two closest competitors combined, according to new research released today.

According to market research firm, iSuppli, Nokia led all mobile handheld makers with 348 million unit shipments in 2006. Its two closest competitors, Motorola and Samsung combined for a total of 335.3 million units shipped.

Nokia shipped a whopping 106 million units in the fourth quarter of 2006, up from 83.7 million during the same period a year earlier. Nokia's highest growth and volume is coming from Europe, which accounted for nearly 32 percent of Nokia's shipments in the fourth quarter, iSuppli said.

Though not the largest by unit shipments, Sony Ericsson made the biggest splash in 2006, posting the largest quarter-over-quarter growth of all mobile-phone makers in its fiscal fourth quarter.

Sony Ericsson’s shipments increased to 74.8 million units in 2006, up 46.4 percent from 51.1 million units in 2005.

Sony Ericsson is targeting its entire product line at the mid-to-high range of the market and just recently has started entering the emerging low-cost handset market, said Tina Teng, wireless communications analyst at iSuppli.