Spectrum auction on Day 4 ended with a meagre addition of Rs 2,531 crore, taking total bids to over Rs 63,500 crore as almost 60 percent of airwaves, including the premium 4G bands of 700 Mhz and 900 Mhz, remained unsold.

At the end of the fourth day, the government received commitments for little over 40 per cent of the total spectrum put on the block. As much as 2,354.55 MHz of frequencies valued at Rs 5.63 lakh crore at the base price have been put up for auction across seven bands.

"Bids worth over ₹63,500 crore have been received until the end of the 23rd round for 956.8 Mhz spectrum, out of total 2,354.55 Mhz put for auction," an official source told PTI.

Bidding will resume tomorrow at 1000 hrs with the duration of each round shrinking to 45 minutes from 60 minutes, the source added.

According to the bid document, the duration of each bidding round is reduced when the number of slots put up for auction, falls below ten slots. The government had put up 126 slots on offer in the current spectrum auction, which was touted to be as the largest spectrum auction ever.

Yesterday, the auction had witnessed an additional bidding of ₹4,097 crore taking the commitments at the end of the third day to ₹60,969 crore.

Seven telecom companies -- Bharti Airtel, Vodafone, Idea Cellular, Reliance Jio, Aircel, Reliance Communications and Tata Teleservices -- are in the fray for acquiring 3G and 4G spectrum, crucial for maintaining a competitive edge in the market and offering next generation services in the world's second-largest telecom market.

There is no demand yet for frequencies in 700 MHz and 900 MHz bands while bidding interest has been seen largely around 1800 MHz and 2300 MHz that can be used by operators to provide 4G services.