China has suspended the Shanghai leg of Ant Group Co.’s $35 billion offering, potentially derailing the world’s biggest initial public offering.

The Shanghai stock exchange will suspend the listing amid changes in the regulatory environment, it said in a statement Tuesday without providing further details. The debut was expected for Thursday, the same day as the Hong Kong portion.

The shock move comes after China’s regulators warned that Jack Ma’s firm faces increased scrutiny and will be subject to the same restrictions on capital and leverage as banks. Ma, Ant’s billionaire co-founder, was summoned to a rare joint meeting on Monday with the country’s central bank and three other top financial regulators.

Ant’s decision to list on the Star board, a market launched in Shanghai last year, was seen as a major win for mainland exchanges. The IPO had sparked a frenzy among individual investors, with about $2.8 trillion worth of subscriptions for the Shanghai leg alone. In the preliminary price consultation of its Shanghai IPO, institutional investors subscribed for over 76 billion shares, more than 284 times the initial offering tranche.

Ant has faced scrutiny in Chinese state media in recent days after Ma criticized local and global regulators for stifling innovation and not paying sufficient heed to development and opportunities for the young. At a Shanghai conference late last month, he compared the Basel Accords, which set out capital requirements for banks, to a club for the elderly.