Asian shares fell on Thursday as the tech sector took a beating on renewed angst about spending on artificial intelligence while investors braced for a wave of central bank meetings set to underscore policy divergence worldwide.

In Hong Kong, the benchmark Hang Seng Index lost 137 points, or 0.54 percent, to open at 25,330.

On the mainland, the benchmark Shanghai Composite Index was down 0.34 percent at 3,857 while the Shenzhen Component Index was 0.85 percent lower at 13,112 and the ChiNext Index, tracking China's Nasdaq-style board of growth enterprises, was down 1.17 percent at 3,138.

Geopolitical tensions are roiling the commodities markets.

Oil prices extended a rebound from five-year lows after US President Donald Trump ordered a "blockade" of all sanctioned oil tankers entering and leaving Venezuela.

Silver hit a new record that helped pull up gold.

Sterling nursed losses after an unexpected drop in UK inflation all but guaranteed a rate cut from the Bank of England later in the day.

The European Central Bank, the Norges Bank and Riksbank are also due to deliver their policy decisions on Thursday, with focus squarely on the outlook as all three are widely expected to hold rates steady.

In the region, traders are bracing for a rate hike in Japan on Friday though there is less certainty about the pace of tightening next year.

MSCI's broadest index of Asia-Pacific shares outside Japan fell 0.5 percent as South Korea dropped 1.3 percent.

Japan's Nikkei was down 1.2 percent.

Nasdaq futures gained 0.3 percent and S&P 500 futures rose 0.2 percent, after a tech-led selloff on Wall Street as investors grappled with renewed concerns over record AI spending.

Shares of AI bellwether Nvidia tumbled 3.8 percent.

Oracle plunged 5.4 percent after it announced an equity deal to support a data center project would not include a key partner Blue Owl Capital.

The stock has shed almost 50 percent from mid-September when a deal with OpenAI sparked a 35 percent one-day rally.

"Oracle remained the primary source of anxiety... This latest setback deepened investor scepticism around Oracle’s aggressive AI infrastructure buildout," said Tony Sycamore, analyst at IG, adding that he has now moved to a more neutral stance on the Nasdaq 100.

"Worries over soaring capex, heavy debt, construction delays, OpenAI's massive cash burn, and mixed Q2 earnings have eroded confidence, positioning Oracle as the poster child of fading AI infrastructure hype."

On the monetary policy front in the United States, Federal Reserve governor Christopher Waller, who is expected to be interviewed by Trump as a candidate for the next Fed chair, said the central bank has room to cut interest rates amid signs of job market weakness.

Investors are also watching out for a US inflation report for November later in the day that will not include the month-on-month measure since a record government shutdown prevented data collection for October.

Forecasts are centred on an annual rise of three percent in core inflation last month. (Reuters/Xinhua)