Asia’s major equity markets closed Thursday’s session split between gains and losses, with China and South Korea coming under pressure from a wave of selling in technology stocks after quarterly results from two sector giants disappointed investors — raising fresh doubts about near-term returns on artificial intelligence trading.

The MSCI Asia Pacific index, the benchmark for Asian equity trading, fell 0.35%, having posted its best session in three months on Wednesday on the back of strong quarterly earnings from SK Hynix. In Europe, futures pointed to a subdued open, with investors focused on the European Central Bank’s monetary policy decision later in the day.

The technology sector faced renewed turbulence as Alphabet shares fell 10% in pre-market trading after the Google parent reported revenues and profits that came in below analyst expectations. Investors fear the company is falling behind in the race to develop artificial intelligence, despite having committed hundreds of billions of dollars to fuel the technology.

Adding to the pessimism were Samsung’s quarterly results. The South Korean company reported chip-division profits below expectations alongside rising AI investment, prompting investors to punish the stock. Samsung fell more than 4%, dragging down the Kospi index — widely regarded as a barometer for the technology sector — which closed the session down 1.37%.

“Expectations were already extremely high, so in a sense, simply meeting forecasts is not enough,” Wataru Akiyama, strategist at Nomura Securities, told Bloomberg. “Unless companies can demonstrate earnings growth that exceeds those already elevated expectations, their shares may fall when they report results,” he added.

Not all the news was negative, however. Microsoft shares surged more than 3% in pre-market trading after the company beat analyst estimates in the first quarter of its fiscal year, with Azure, its cloud computing platform, growing 48% and capital expenditure coming in below forecasts.

Investor attention now turns to Amazon’s results, due after the close of Wall Street on Thursday, and to Apple’s figures the following day. Also in focus is the widely anticipated decision by the US Federal Reserve to hold interest rates unchanged — a move expected to be mirrored by the ECB when it rules on monetary policy later in the day.

Among the main moves by market, China’s Hang Seng and Shanghai Composite indices fell 0.5% and 0.82% respectively, even after the government announced it was mobilising state-linked investment funds to stem the decline in equity markets. Japan’s Nikkei 225, meanwhile, gained 1.10% and Australia’s ASX 200 rose 0.5%.