Google's Android operating system (OS) has continued its dominance in the smartphone market with a more than 50 percent share.

According to figures from research firm Gartner, Android accounted for 56.1 percent of the smartphone market in the first quarter of the year compared to 36.4 percent a year ago. Its closest rival, Apple's iOS, managed to get a 22.9 percent share, an increase from the 16.9 percent of last year. See also: Group test: what's the best smartphone?

Google and Apple saw shipments grow in the first quarter to 81 million units and 33.1 million units, respectively. Devices like the Samsung's Galaxy S3 suggest this figure will increase, too.

The overall smartphone sector grew 44.7 percent year-on-year to 144.4 million units even though the worldwide sales of mobile phones dropped 2 percent.

The numbers were more bad news for Nokia and Research in Motion, confirming again that Nokia lost the top mobile phone vendor spot to Samsung. RIM saw shipments drop 3.1 million units and its BlackBerry OS only accounted for 6.9 percent of the smartphone market.

Nokia's Symbian OS droppedits share by nearly 20 percent down to 8.6 percent and it's now favoured Windows Phone made up 1.9 percent of the smartphone market. The Bada OS was the only one to see a growth other than Android and iOS, gaining 0.8 percent.

The firm said the smartphone market has become highly commoditized and differentiation is becoming a challenge for manufacturers.

"This is particularly true for smartphones based on the Android OS, where a strong commoditization trend is at work and most players are finding it hard to break the mould," said Anshul Gupta, principal research analyst at Gartner.