Global personal computer (PC) sales fell 8.6 percent in the third quarter from a year ago due to gloomy economic sentiment and the shift to tablets and smartphones, an industry report said Thursday.

Potential buyers were also holding back for the expected release in the fourth quarter of Microsoft's Windows 8 operating system, US-based technology research firm IDC said in a statement.

Sales of PCs in the July-September quarter totalled 87.8 million units, down from 96.08 million in the same period in 2011, tumbling more steeply than IDC's forecast of a 3.8 percent contraction.

"PCs are going through a severe slump," said Jay Chou, a senior analyst with IDC's Worldwide PC Tracker.

"The industry had already weathered a rough second quarter, and now the third quarter was even worse."

David Daoud of IDC said alternative devices like tablets continued to eat into the PC market.

"In addition, businesses have slowed their refresh cycle as they remain concerned about the broad economic outlook," Daoud said.

The International Monetary Fund has cut its global economic growth forecasts for this year and next, while the World Bank and Asian Development Bank has also slashed projections for Asia.

IDC said computer sales in the Asia-Pacific region outside Japan contracted year-on-year in the third quarter, but did not give figures.

"China was mostly on target but the rest of the region came in below expectations as ongoing economic sluggishness and competing device distractions weighed on PC spending," IDC said.

US-based Hewlett-Packard narrowly retained its position as the world's top PC vendor with a 15.9 percent market share during the quarter, IDC said.

Chinese manufacturer Lenovo was a close second with a 15.7 percent market share, followed by Dell with 10.8 percent.