Asian stocks tumbled in early trading on Monday as investors reined in risk-taking at the start of a week sprinkled with central bank decisions and data releases.

In Hong Kong, the benchmark Hang Seng Index opened down 258 points, or 1 percent, at 25,718.

The benchmark Shanghai Composite Index was down 23 points, or 0.62 percent, at 3,865 while the Shenzhen Component Index was 107 points, or 0.81 percent, lower at 13,150 and the ChiNext Index, tracking China's Nasdaq-style board of growth enterprises, was down 1.16 percent at 3,157.

The losses came hours after the 225-issue Nikkei Stock Average in Tokyo opened down 484 points, or 0.95 percent, at 50,352.

The MSCI's broadest index of Asia-Pacific shares outside Japan was down 0.6 percent, led by a drop of up to 2.7 percent in South Korean shares, one of the world's best-performing markets this year.

"We roll into the final week of trading for 2025 before many square off their books and call it a year," said Chris Weston, head of research at Pepperstone Group in Melbourne.

"Some will have already done so," he added.

"One suspects liquidity conditions will thin out this week from what is typical, but remain sufficient for size to be worked without excessively moving prices, but will then really drop next week."

S&P 500 e-mini futures were up 0.1 percent , while the yield on the US 10-year Treasury bond held steady at 4.184 percent , as investors awaited a string of economic data releases and a slew of decisions from central banks.

Among the central banks making decisions this week, the Bank of Japan is expected to hike rates by 25 basis points to 0.75 percent while the Bank of England may make an equal-sized cut to 3.75 percent. The European Central Bank is expected to keep interest rates on hold, alongside Sweden's Riksbank and Norway's Norges Bank.

Investors will also have the chance to check in on a host of economic data that were delayed by the US government shutdown, including the jobs report for November and the monthly consumer price index. (Reuters/Xinhua)