NEW DELHI - The underseas cable arm of Indian mobile giant Reliance Communications has filed a prospectus for an IPO in Singapore in a step that could raise US$1 billion (S$1.3 billion) for its debt-strapped parent.

Sources earlier said the company, owned by Indian billionaire Anil Ambani, hoped to raise the amount from the initial public offer (IPO) to retire costly debt.

However, a Reliance spokesman described the billion-dollar figure as "speculation".

Reliance Communications, which has long been seeking to raise funds to cut its hefty debt burden of around US$7 billion, said in a statement it would "provide subsequent updates to the stock exchanges in due course".

Last month Singapore authorities said Reliance could list its underseas unit on the Singapore stock exchange as a trust. The appeal of such trusts lies in regular dividend flows.

Reliance's new Global Telecommunications Infrastructure Trust has now filed the prospectus with the Monetary Authority of Singapore.

Under the trust's rules, Reliance, India's second-largest mobile operator by customers, must sell off between 51 per cent and 75 per cent of its underwater cable unit's assets.

The assets being sold are part of Reliance's purchase of bankrupt Flag Telecom nearly a decade ago. The network's fibre optic cables carry communication signals across Asia, the Middle East, Europe and the United States.

Reliance Communications has been hit by strong competition in India's congested mobile market and has seen its profits steadily decline.