Commuters travel past commercial buildings on a tram in the Central district of Hong Kong on June 21, 2021. (ANTHONY WALLACE / AFP)

Hong Kong shares finished down on Tuesday to a more than one year low, after US drugmaker Moderna set off fresh alarm bells about the Omicron variant, with tech firms dragging down the Hang Seng Index.

The Hang Seng index was down 1.6 percent at 23,475.26, while the China Enterprises Index lost 1.5 percent to 8,368.49 points.

For the month, the Hang Seng index dropped 2.5 percent while the China Enterprises Index declined 2.4 percent.

Hong Kong shares extended losses in afternoon trade after the head of Moderna told the Financial Times that COVID-19 vaccines are unlikely to be as effective against the Omicron variant of the coronavirus as they have been against the Delta variant.

Hong Kong shares extended losses in afternoon trade after the head of Moderna told the Financial Times that COVID-19 vaccines are unlikely to be as effective against the Omicron variant of the coronavirus

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The Hang Seng Tech Index lost 1.2 percent.

"Uncertainties in the tech sector haven't fully receded in the short term as some firms were fined recently," said David Huang, senior investment srategist at AllianceBernstein.

"But it doesn't mean those firms will not have opportunities in the future, as the society still needs them," said Liang Zhu, chief investment officer at AllianceBernstein.

Zhu added that investors require a higher risk premium for the shares, so their prices should be corrected to a more reasonable range.

Alibaba's HK shares fell 2.1 percent to their lowest since listing. Fellow online giant Tencent slipped 0.7 percent and food delivery company Meituan extended Monday's tumble by another 2.9 percent to hit an almost eight-week low.

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Macao gambling firm Suncity Group Holdings Ltd's shares almost halved in resumed trade after CEO Alvin Chau was arrested on Sunday. 

Casino operators Sands China, Galaxy Entertainment and Wynn Macau also extended losses. This year, HK-listed gambling stocks have lost more than 40 percent.