Sunil Mittal, the chairman of Bharti Airtel, appeared in a Delhi court today that's investigating alleged corruption in allocating mobile phone bandwidth.
Shyamal Ghosh, a former secretary of the Department of Telecommunications, and Ravi Ruia, one of the founders of diversified conglomerate Essar Group, also appeared in the court today.
The Supreme Court of India had deferred a decision on Monday on whether Mr Mittal could be summoned.
Last month, a lower court investigating the assignment of mobile network licenses and airwaves had asked the billionaire to appear before it on April 11. The case also involves former executives in two firms that are now part of Vodafone Group's Indian unit.
Mr Mittal is seeking to dismiss the case. The Supreme Court will hear the case again on Monday.
The CBI in December charged Bharti Airtel and the two companies that are now part of Vodafone's Indian unit over alleged irregularities in obtaining mobile phone airwaves in 2002, but did not name any company executive.
Last month, the New Delhi court summoned Mr Mittal, Mr Ghosh, Mr Ruia and Asim Ghosh, the former head of Vodafone's Indian unit, saying the executives "represent the directing mind and will of each company". None of the executives has been charged.
Vodafone, which entered India in 2007, has previously declined to comment on the case. Essar Group has said it was looking into legal proceedings to challenge the court's order.
With inputs from Reuters