WASHINGTON - Apple’s iPad and other Internet-connected media tablets are draining demand for laptops and notebook computers, research firm Gartner said Thursday, sharply lowering its worldwide PC forecast this year.

Consumers are diversifying their computing across a raft of new mobile devices, ending five years of strong growth in demand for the portable PCs, Gartner said.

Worldwide PC shipments are expected to reach 387.8 million units in 2011, a 10.5 percent increase from 2010, the firm said, lowering its previous forecast of 15.9 percent growth.

For 2012, PC shipments of 440.6 million units would represent a 13.6 percent rise from 2011, down from the prior estimate of 14.8 percent.

"These results reflect marked reductions in expected near-term unit growth based on expectations of weaker consumer mobile PC demand, in no small part because of the near-term weakness expected in China’s mobile PC market, but also because of a general loss in consumer enthusiasm for mobile PCs," Ranjit Atwal, research director at Gartner, said in a statement.

Over the past five years, sales of laptops and notebooks have driven the personal computer market with average annual growth rates nearing 40 percent, the firm noted.

"However, due to the spread of low-cost embedded Wi-Fi modules, Internet access is now available through a multitude of mobile devices that allow consumers to engage in virtually all their favourite online activities without the need of a mobile PC," Gartner said.

Sales of consumer mobile PCs in mature markets were projected to average 10 percent annual growth from 2011 through 2015.

Worldwide, the professional market was expected to continue to show double-digit growth in 2011 and 2012 as aging PCs are replaced.

"However, even in the professional market, media tablets are being considered as PC substitutes, likely at least delaying some PC replacements," said Raphael Vasquez, senior research analyst at Gartner.