Taiwan's Acer and Asus and China's Lenovo posted strong growth as personal computer sales surged more than 20 percent in the second quarter over a year ago, market research company Gartner said.

Gartner said worldwide PC sales increased 20.7 percent in the quarter to 82.9 million units. Another research group, the International Data Corporation (IDC), said they rose 22.4 percent over a year ago.

"The preliminary second quarter results indicate ongoing improvement of the PC market," Gartner principal analyst Mikako Kitagawa said.

IDC research analyst Jay Chou said the PC market "remains robust, and in a recovery phase, despite challenges to a broader economic recovery, such as slow job growth and a more conservative outlook in Europe and Asia-Pacific."

IDC vice president Bob O'Donnell said "the surge in consumer activity seen in the past two quarters has started to slow as expected, while commercial replacements continue to grow.

"We expect consumer activity to remain healthy, but gradually slow through the end of the year, while commercial market growth will be more stable," he said.

Gartner said US computer giant Hewlett-Packard remained the worldwide leader in PC sales but its year-on-year growth rate of 12.3 percent came in below the industry average of 20.7 percent.

HP's market share slipped to 17.4 percent from 18.8 percent a year ago.

Acer saw year-on-year growth of 31.6 percent and its market share increased to 13 percent from 12 percent.

Dell notched up 19-percent growth but its market share slipped to 12.4 percent from 12.6 percent and Gartner said the consumer market was "still a challenge" for the Texas-based company.

Lenovo posted year-on-year growth of 47.2 percent and increased its market share to 10 percent from 8.2 percent.

Asus registered the most spectacular growth -- 78.5 percent -- and the company leapfrogged Japan's Toshiba, grabbing a 5.2 percent market share, up from 3.5 percent a year earlier.

Toshiba posted a growth rate of 10.7 percent and slightly increased its market share, to 5.1 percent from 4.8 percent.

Gartner's Kitagawa said sales of mini-notebooks or netbooks -- low-cost, bare-bones laptop computers -- "slowed significantly" in the second quarter, an indication the market was maturing.

"Mini-notebook shipment growth still exceeded growth rates of the overall mobile PC market, but mini-notebook growth slowed to the low 20 percent range compared with more than 70 percent in the last two quarters," Kitagawa said.

"Surging popularity of Apple's iPad temporarily cannibalized mini-notebooks, as well as consumer notebook sales to some degree," she said. "It is not certain at this stage if the cannibalization will continue."