While Apple increased its iPhone sales year over year, its share of the global smartphone market shrank to 18.2 percent in the first quarter, according to data from Gartner.

Apple fell from its 22.5 percent share a year ago, the new figures released on Tuesday show. Meanwhile, Apple's chief rival Samsung increased its market share from 27.6 percent a year ago to 30.8 percent in the first quarter of 2013.

In fact, Apple was the only company among the top five smartphone vendors to see its share shrink. Third-place LG Electronics grew from 3.4 percent in 2012 to 4.8 percent in 2013, while Huawei Technologies grew to 4.4 percent, and ZTE took a 3.8 percent share.

Success seen by Android handset makers helped Google's mobile platform take a commanding 74.4 percent lion's share of the smartphone market. The iPhone is the only smartphone on which Apple's iOS is available, and so its second-place platform share of 18.2 percent was identical to its hardware market share.

"Apple is faced with the challenge of being increasingly dependent on the replacement market as its addressable market is capped," said Anshul Gupta, principal research analyst at Gartner. "The next two quarters will also be challenging, as there are no new products are expected to be coming before the third quarter of 2013."

In all, global smartphone sales grew from 147 million a year ago to 210 million in the first quarter of 2013. Smartphones accounted for 49.3 percent of all mobile phone sales worldwide, up from 34.8 percent in the first quarter of 2012.