SINGAPORE — Asia-Pacific markets traded mixed Thursday as investors assessed risks surrounding the omicron Covid variant.

The Nikkei 225 in Japan declined 0.22% while the Topix index fell 0.33%.

In Australia, the ASX 200 traded flat but the energy and materials subindexes were down 0.7% and 0.36%. Shares of major miners Rio Tinto and BHP fell 0.69% and 0.82%, respectively.

South Korean shares advanced, with the benchmark Kospi up 0.33% and the Kosdaq higher by 1.16%.

Chinese mainland shares also traded higher. The Shanghai composite rose 1.03% and the Shenzhen component added 1.27%.

Hong Kong shares also advanced as the main Hang Seng index added 0.89% while the tech-focused Hang Seng Tech index rose 2.05%.

Trading in shares of Macao’s Suncity Group and its unit Summit Ascent Holdings were suspended. The Hong Kong stock exchange did not give further details on the suspension. That comes days after Suncity’s chief executive was arrested over alleged links to cross-border gambling, Reuters reported.

Hong Kong-listed shares of major Chinese tech companies advanced. Shares of Alibaba rose 1.82%, Baidu was up 0.83%, Meituan added 1.06% and Tencent was up 1.16%.

Stateside, the major averages posted a third consecutive day of gains while European shares closed lower.

“After a solid run in the previous two days, equities are taking a breather with European shares closing lower amid concerns over the need for a new round of covid restrictions,” Rodrigo Catril, senior foreign-exchange strategist at the National Australia Bank, said in an early morning note.

Investors are keeping an eye on the omicron Covid variant, which has rattled markets in recent weeks.

The World Health Organization on Wednesday said the variant could change the course of the pandemic. Scientists worldwide are scrambling to determine just how contagious and lethal omicron is and how effective would existing vaccines be against the virus.

While preliminary evidence from South Africa, where the variant was first identified, may suggest that omicron is milder than the delta strain, WHO’s technical lead on Covid-19 says it is “too early to conclude” that.

Meanwhile, Pfizer’s CEO said people might need a fourth Covid-19 shot sooner than expected. That came after preliminary research showed the omicron variant can undermine protective antibodies generated by the vaccine the company developed with BioNTech.

The vaccine makers released results from an initial lab study on Wednesday that showed a third dose of vaccine is effective at fighting the omicron variant while the initial two-dose vaccination series dropped significantly in its ability to protect against the new strain.

The U.S. dollar recovered slightly against a basket of its peers — the dollar index rose 0.11% to 96.004 from its previous close at 95.984.

The Japanese yen was relatively flat, changing hands at 113.67 per dollar while the Australian dollar traded fractionally lower at $0.7170.

Oil prices advanced overnight as the global benchmark Brent settled above $75 a barrel.

During Asian trading hours Thursday, prices also climbed. U.S. crude traded 0.87% higher at $72.99 while Brent rose 0.67% to $76.33.

“Crude oil extended recent gains as inventories fell and concerns ease about the impact of Omicron on consumption,” ANZ Research analysts said in a morning note.

“Pfizer and BioNTech said initial lab studies show a third dose of their vaccines restores protection against the new variant. This has seen Brent crude rally more than 9% over the past two days as the market reassesses the likely impact on demand,” the analysts said. Still, risks to demand have not entirely diminished, they added.