Shipments of iPhone devices are expected to top 50 million units in the first quarter of 2015, increasing 14.4% from 43.7 million units shipped in the year earlier period, according to an estimate by sources in Taiwan's handset supply chain.

The estimate comes after Apple reported that it shipped 74.5 million iPhone devices in the fourth quarter of 2014, accounting for 51.2% of its total revenues of US$74.6 billion recorded in the quarter.

Demand for smartphones in the Greater China area during the upcoming Lunar New Year holidays will maintain sales of iPhone devices in the first quarter, the market watchers said.

Apple's sales in the Greater China area, mainly China, Hong Kong and Taiwan, totaled US$16.1 billion in the fourth quarter of 2014, increasing 70% from a year earlier, according to company data.

The ratio of Asia-Pacific sales to Apple's total sales is expected to continue to rise, said the watchers.