NEW DELHI: State-run Coal India said on Tuesday its giant initial public offering, set to raise billions of dollars and possibly become India's biggest ever share sale, is due to start in October.

The country's largest coal miner plans to sell 10 percent of its government-held equity as part of New Delhi's plan to raise a record $8.5 billion from asset sales by March next year.

The IPO will start on October 18 for four-days, company chairman Partha Bhattacharyya told reporters on Tuesday.

Bankers have estimated that the issue could raise more than $3 billion.

Roadshows to attract large investors will start next month, with the aim of attracting global interest from the United States, Europe and Southeast Asia, Bhattacharyya added.

India's largest IPO so far is the $2.46 billion raised by billionaire Anil Ambani's Reliance Power in January 2008, according to the Prime Database, which tracks share offerings in India.

The government's disinvestment policy, outlined in its national budget in February, aims to raise funds that will be used to help the millions in India who live in desperate poverty and bring down the country's fiscal deficit.

Plans have been put forward to sell 20 percent in Hindustan Copper Limited -- 10 percent through fresh equity and another 10 percent through stake sales.

Between 2004 and 2009, the Congress-led government was forced to put disinvestment plans on hold in the face of strong opposition from Communist party allies in the coalition government.

India is the world's third-biggest producer of electricity from fossil fuel and appears set on coal for its future energy needs as the economy develops.

The ministry overseeing the industry maintains that coal will continue to take "centre stage of India's energy scenario" in the years to come.