Ahead of what's likely to be the world's largest initial public offering, China's Ant Group Co. is asking lead bankers to personally sign confidentiality pacts and pressing some investors to explain why they should be allowed to attend marketing meetings, sources familiar with the matter said.

In doing so, Ant is following a highly unusual process that draws on some of the tactics its former parent and affiliate Alibaba Group Holding Ltd. has previously used.

Other unique measures taken by Ant include dividing up the underwriting work for what could be a $35 billion (¥3.69 trillion) offering among several banks such that no one firm has the full picture of the process, four sources with direct knowledge of the matter said.