Hong Kong stocks continued their upward trend on Monday, buoyed by optimism surrounding China's stimulus package aimed at rescuing the property market.

The Hang Seng Index jumped 2.43%, or 501.38 points, to close Monday's session at 21,133.68. The Hang Seng China Enterprises Index also jumped 2.88%, or 209.89 points, to close at 7,509.79.

Investors shrugged off weak manufacturing data as they focused on the potential benefits of Beijing's stimulus package.

China's composite purchasing managers' index, a measure of overall activity in the manufacturing and services sector, increased to 50.4 in September from 50.1 in August, according to data from the National Bureau of Statistics on Monday.

Growth in China's services sector decelerated at the end of the third quarter due to a marginal rise in incoming new business and activity, while China's manufacturing sector returned to contractionary territory in September after seeing improvement in August as new orders and exports fell during the month.

The weak business activity data was overshadowed by the People's Bank of China's move to infuse 182 billion yuan in seven-day reverse repo operations with a 1.5% rate to ensure adequate liquidity by the end of the quarter. The Chinese central bank also tweaked its pricing mechanism for interest rates of individuals' commercial housing mortgages.

In corporate news, Qiniu (HKG:2567) launched its initial public offering in Hong Kong, seeking to raise up to HK$456.9 million.

Alphamab Oncology (HKG:9966) unit Jiangsu Alphamab Biopharmaceuticals signed a licensing agreement with Shanghai JMT-Bio Technology, a unit of CSPC Pharmaceutical Group (HKG:1093), to develop, sell, and commercialize tumor-related drug JSKN003 in mainland China. Alphamab's shares rose over 54% on Monday's close.

Bairong (HKG:6608) plans to expand its share repurchase program and extend the repurchase period until May 31, 2025. The company's shares closed nearly 18% higher on Monday.