Poor computer sales have led both computer maker Apple and chip maker AMD to cut their earnings forecasts.

Apple said it expected to report revenues of between $1.4-1.45bn (�937m) for the April to June period, down from its earlier forecast of $1.6bn.

We are experiencing a slowdown in sales

Steve Jobs, Apple chief executive

Meanwhile AMD said it was set to report a "substantial operating loss" for its latest financial quarter.

The warnings shocked Asian stock markets into steep falls on Wednesday: Tokyo's benchmark Nikkei index closed down 3.3% at 10,476.18.

Shares in both companies fell after the close of trade in the US on Tuesday.

Apple suffers

Apple said its earnings shortfall was due to poor sales to consumers, and to advertising and publishing businesses.

The company said sales were "particularly weak" in Europe and Japan.

Apple is best known for its unique designs, such as the iMac computer, and its iPod portable music player.

But the distinctive look of its products has failed to protect the company from the slowdown in computer sales.

"Like others in our industry, we are experiencing a slowdown in sales this quarter," said company chief executive Steve Jobs.

"As a result, we're going to miss our revenue projections by around 10%, resulting in slightly lower profits."

But Mr Jobs said he remained upbeat about future prospects.

"As one of the few companies currently making a profit in the PC business, we remain very optimistic about Apple's prospects for long-term growth," he said.

Shares in Apple fell to $19.13 in after-hours trade, down from Tuesday's close of $20.15.

AMD woe

The downturn in the PC market has also hit the world's number two chip maker AMD.

The company said it now forecast sales of between $620-700m for the latest quarter, down from a previous projection of $820-900m.

"As we have seen in previous statements from a number of other companies, there is a broad weakness in the personal computer market and it is adversely affecting AMD," said AMD's chief financial officer Robert Rivet.

Shares in AMD fell to $8.50 in after-hours trading, having closed at $10.30 on the New York Stock Exchange.

Shares in rival chip maker Intel also fell, sliding to $21.32 from $22.02.