Asian stock markets fell sharply on Friday, led by a sell-off in technology firms as investors worried that recent jumps in share prices had gone too far.

Trading on South Korea’s Kospi was temporarily halted as an 8% fall in the benchmark index triggered a mechanism intended to curb panic selling. The index closed 5.8% lower.

It comes after shares in Apple fell sharply on Thursday after it announced it would raise the prices of its iPads and MacBooks due to the soaring cost of computer chips.

Some investors are also concerned about the hundreds of billions of dollars being spent this year by big tech firms to build artificial intelligence (AI) infrastructure.

Traders are reassessing the valuations of tech stocks, while some are taking profits after a rally in recent months, said senior partner David Makaryan from the Alpha Pacific Group, an investment firm.

“The long term investment case for AI remains compelling, but investors are becoming far more selective about which companies can justify the valuations the market has assigned to them,” Makaryan said.

Elsewhere in Asia, Japan’s Nikkei 225 closed more than 4% lower as shares in technology investment giant SoftBank fell by 12.5%.

Other major indexes in the region, including Taiwan and mainland China, were also sharply lower.

Share trading in South Korea has been particularly volatile in recent months.

Friday’s 20-minute halt on the Kospi marked the third time the so-called circuit breaker has been triggered this week and the fifth such event this year.

On Thursday in the US, Apple shares dropped by 6% – its biggest one-day fall in more than a year.

Microsoft shares also fell after it announced higher prices for its Xbox gaming consoles, citing higher costs of components.

The moves have raised concerns that rising component prices hit sales of devices, which in turn may slow demand for computer chips.

The high cost of commercialising AI tools is gradually being passed on to consumers, said analyst Raymond Woo from Kyoto University Innovation Capital.

That “naturally raises questions” about how quickly demand for such tools will match the investment into AI, and whether the valuations of tech stocks today are realistic, Woo said.