Asian stocks were mostly flat Thursday in cautious holiday trade following a mixed close on Wall Street, though Chinese artificial intelligence start-up SenseTime was a big winner with a 23 percent jump on its Hong Kong debut.

Fears of the Omicron coronavirus variant are still weighing on markets, with the United States hitting its highest-ever seven-day average of new Covid cases and the World Health Organization warning that a "tsunami" of infections would push health systems to the brink of collapse.

But investors have also clung to data showing a reduced risk of hospitalisation from Omicron, and the fact that trading volumes are extremely low in the period between Christmas and the New Year.

"Despite global surges in Covid cases, the markets are reflecting the new reality that Covid is here to stay albeit more on our terms than its," Kevin Philip, managing director at Bel Air Investment Advisors, said in an email.

Next year, he added, "we are facing less of a Covid-influenced world, and a return toward normalcy."

Tokyo was marginally down at the close on its last trading day of 2021, but the benchmark Nikkei index rose nearly five percent for the year to its highest annual close since the 1989 boom.

– 'Lethargic' trade –

Hong Kong and Shanghai both closed slightly higher.

SenseTime was among stocks bucking the trend, with its price well up only a week after it was blacklisted by the United States over accusations of genocide in Xinjiang.

The sale boosted the wealth of company co-founder Tang Xiao'ou. The MIT alum's wealth jumped by $500 million to roughly $3.9 billion, according to the Bloomberg Billionaires Index.

Also in Hong Kong, shares in embattled Chinese property giant Evergrande tumbled 10 percent after a report that the group had failed to meet two more offshore payments.

But markets were mostly sedate overall.

Seoul and Taiwan recorded small dips, while Wellington and Manila were slightly up.

"Ahead of year-end and New Year holidays, the number of market participants is low and trade will likely remain lethargic," Mizuho Securities said.

"Asia is having a mixed day… and it appears that some pre-New-Years-Eve book squaring is weighing on some markets," said Jeffrey Halley, a senior market analyst with OANDA.

Things were similarly quiet at the open in Europe.

London fell 0.2 percent, Frankfurt's was down 0.1 percent and Paris was fractionally lower.

– Key figures around 0820 GMT –

Tokyo – Nikkei 225: DOWN 0.40 percent at 28,791.71 (close)

Hong Kong – Hang Seng Index: UP 0.11 percent at 23,112.01 (close)

Shanghai – Composite: UP 0.62 percent at 3,619.19 (close)

London – FTSE 100: DOWN 0.2 percent at 7,409.29

New York – S&P 500: UP 0.1 percent at 4,793.06 (close)

Euro/dollar: DOWN at $1.1308 from $1.1347

Pound/dollar: DOWN at 1.3466 from $1.3499

Euro/pound: DOWN at 83.97 pence from 84.06 pence

Dollar/yen: UP at 115.16 from 115.01 yen

West Texas Intermediate: UP 0.37 percent at $76.28 per barrel

Brent North Sea crude: DOWN 0.34 percent at $78.96 per barrel

— Bloomberg News contributed to this report —

burs-leg/qan

SenseTime

China Evergrande Group

MIZUHO FINANCIAL GROUP