Ant, backed by Chinese e-commerce giant Alibaba, plans to list simultaneously in Hong Kong and on Shanghai's STAR Market, in what sources have said could be the world's largest IPO and come as soon as October.

Under the local rules, once Ant goes through the STAR Market listing committee's hearing, it can then register the flotation with the Chinese securities regulator and wait for the registration to be accepted before starting the pricing consultation process.

Ant has addressed questions raised by the Shanghai exchange over its planned IPO, as per disclosures on the bourse website on Monday and Wednesday. The firm can seek listing approval from the exchange after the bourse is satisfied with its responses.

The Shanghai exchange had earlier sought explanations from the company about its relationship with Alibaba, how regulatory changes will impact business, and comparable peers in domestic and overseas markets.

According to its filing earlier on Wednesday, Ant said that although its Alipay arm was set up by Alibaba, the two firms have reached strategic partnerships and have pledged not to compete with each other.

Alipay, Ant's biggest and best-known business, is the largest player in China's 430 trillion yuan ($62 trillion) third-party mobile payments market, according to market researcher Qianzhan.

The IPO of Ant, already the world's most valuable unicorn - or billion-dollar unlisted tech firm - would be the first simultaneous listing in Hong Kong and Shanghai's year-old STAR Market.

If Ant completes the offering at the around the $30 billion upper end of expectations, it would rival oil giant Saudi Aramco, which raised $29.4 billion last December, surpassing the record set by Alibaba's $25 billion flotation in 2014.

(Reporting by Julie Zhu and Samuel Shen; Writing by Sumeet Chatterjee; Editing by Kevin Liffey and Mark Potter)