China's mammoth firms Alibaba, JD.com, Nio, Baidu, Gaotu Techedu and Bilibili were down between 4.5% and 6% in premarket U.S. trading.

Exchange-traded funds exposed to Chinese securities also suffered heavy losses with iShares China Large-Cap ETF, iShares MSCI China ETF, KraneShares CSI China Internet ETF and Invesco China Technology ETF down between 3% and 7%.

China posted a steep jump in daily COVID-19 infections on Tuesday, with new cases more than doubling from a day earlier to hit a two-year high, raising concerns about the rising economic costs of its tough measures to contain the disease.

JPMorgan Chase & Co downgraded 28 Chinese stocks listed in the United States and Hong Kong on Monday, sending the tech giants listed in Hong Kong tumbling more than 8% on Tuesday.

"As the Russia-Ukraine conflict continues, we believe global investors are increasingly nervous about geopolitical risks to China as more and more country and corporates impose sanctions on Russia," JPMorgan Chase & Co said.

There were also concerns that China could decide to provide economic support for Russia which is being hit by sanctions for its invasion of Ukraine.

The Hang Seng index fell 5.7% to 18,415.08, the lowest since Feb. 12, 2016. The China Enterprises Index <.HSCE lost 6.6% to 6,123.94, the lowest since Oct. 29, 2008.

The Hang Seng benchmark marked its worst day since July 2015 in the decade's busiest trading day.

The Hang Seng Tech Index has lost roughly 22% since last Friday, as the U.S. Securities Exchange Commission identified Chinese companies that will be delisted if they do not provide access to audit documents.

"In the near term, it's a policy-driven market and the policy hasn't changed in our view to become more constructive on Chinese stocks," said Andrea Cicione, head of strategy at TS Lombard.

(Reporting by Eva Mathews in BENGALURU and Julien Ponthus in LONDON; Editing by Saikat Chatterjee and Nick Macfie)