By Xie Yu

Chinese shares jumped, with the flagship Shanghai Composite Index hitting its highest since early 2018, as small investors bet that a recovering economy and easier financial conditions would fuel a boom in corporate profits.

The index gained 5.7% to 3332.9, its biggest one-day gain since 2015. Brokerages, banks, miners, aviation companies and developers led the rally. Citic Securities, a leading brokerage firm, rose 10%--the maximum daily move allowed in China. Industrial and Commercial Bank of China, the country's biggest commercial bank, soared 8.5%.

Khiem Do, head of Greater China investments at Barings in Hong Kong, said a similar dynamic was at play as that seen in the U.S., where stuck-at-home individuals have flocked to the stock market to make money.

"We feel great passion from individual investors, a bit like what fueled the bull run in the year of 2015," he said, recalling an earlier run-up in Chinese stocks.

By early afternoon, turnover across the Shanghai and Shenzhen markets topped 1.28 trillion yuan ($181 billion). That was almost double the average of daily turnover at 625 billion yuan in May, according to the latest available monthly data from Chinese exchanges.

Monday's rally built on a strong end to last week, with the Shanghai Composite rising more than 2% on both Thursday and Friday.

Official data last week showed China's economic recovery picked up steam in June, as exports and services benefited from government-support policies and the reopening of some overseas markets.

Joanne Chiu contributed to this article.

Write to Xie Yu at Yu.Xie@wsj.com