Shares soared Tuesday in Shanghai as Chinese markets reopened after a weeklong holiday but then gave up a chunk of their initial gains as officials in Beijing outlined details of plans to revive the world's second-largest economy.

On Tuesday, hashtags about mainland China's stock market — including the apt #A-shares rollercoaster — rushed to the top of Weibo's trending list. A-shares are stocks of Chine

China's stock markets roared back from a week-long break and climbed to their highest levels in more than two years at the open, but lost steam after officials failed to inspire confidence in stimulus plans intended to turnaround a sputtering economy.