Apple increased its dominance of the tablet market in the second quarter, boosting its market share of units shipped to almost 70 percent, IDC said Thursday.

Apple shipped 17 million iPads, upping its share to 68.2 percent from 61.5 percent in last year’s second quarter, when it shipped 9.24 million units. Year-on-year, Apple grew its second-quarter iPad shipments 84.3 percent.

Worldwide tablet shipments for the second quarter were approximately 25 million units, compared to 15 million during the same period in 2011, an increase of 66.2 percent, according to IDC.

The vast majority of consumers continue to favor the iPad, and Apple is also seeing more interest in the device from vertical markets such as education, according to IDC. While shipments are beginning to slow in mature markets, the iPad is experiencing strong sales growth in other regions.

Samsung came in second with almost 10 percent market share. Its tablet shipments grew 117.6 percent year-on-year, and ended up at 2.4 million units.

The success of the Kindle Fire has made Amazon the third largest tablet vendor. The company rebounded from a slow first three months of 2012 to ship 1.25 million units, which was enough to grab a 5 percent market share.

Asus and Acer ranked fourth and fifth, respectively.

For Asus it was a good quarter. It increased shipments by 115.5 percent to 885,000 tablets.

Meanwhile, Acer was the only one among the biggest vendors to see a year-on-year sales drop. The company shipped 385,000 units during the second quarter, compared to 629,000 units a year ago, an almost 40 percent drop.

Competition in the tablet space will heat up in the second half of 2012 with major new products expected from Amazon, Apple and a variety of vendors making tablets based on Microsoft’s new Windows 8 and Windows RT OSes.

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