The benchmark Hang Seng Index ended at 18,664.88 points.
The China Enterprises index of Hong Kong-listed shares in mainland companies, fell 5.1 per cent to 8,528.46, its lowest close since November 29. The decline was the worst one-day percentage loss since May 22.
Rest of the region
Markets in Australia, the Philippines, India and South Korea were all down sharply, continuing their slide from last week, when a nine per cent plunge in Chinese stocks triggered a drop on Wall Street and other global markets.
Analysts said the declines could continue for at least a while longer.
Jose Vistan, research director at AB Capital Securities, said: "It still looks bad tomorrow, since the drop in the Asian markets may pull down markets in Europe and the US later in the day ... It's snowballing."
The Korea Composite Stock Price Index fell for a fourth day, sinking 2.7 per cent, while Australia's benchmark S&P/ASX200 index fell for a fifth day, tumbling 2.3 per cent. In India, the market opened 3.7 per cent lower.
"Basically, the fall is because global markets are seeing a down trend," said Devina Mehra of First Global, a brokerage firm in Mumbai, India.
She said the fast rise in India's market in recent years was "overdone and expectations were too high".
In China, the Shanghai Composite index fell a more modest 1.6 per cent, but foreign-currency denominated "B shares" tumbled after officials denied rumors those stocks might be merged with the mainstream Chinese-currency "A shares".
A lack of market-boosting news as the Chinese national legislature began its annual session also appeared to sap buying enthusiasm.
The yen's recent surge hit Japanese exporters including Canon, Sony and Toyota as share price fell.
Dip in oil prices
Oil prices also fell more than one per cent to below $61 on Monday after mounting losses in Asian stock markets stoked concerns over economic growth, prompting investors to pull back from riskier assets.
US crude was down 66 cents to $60.98 a barrel by 0746 GMT, extending Friday's 36-cent drop - the market's first fall after a seven-session rally built on signs of shrinking US petrol stockpiles and Iran's standoff with the West.
London Brent crude fell 68 cents to $61.40.
Oil, which rose half a dollar last week as traders shrugged off the turmoil that hit other markets, appeared on Monday to be succumbing to the global flight from risk that caused US stocks to suffer their worst week in more than four years.