New Delhi (CNN Business) The battle for India's online shoppers has triggered a smartphone gold rush.

Flipkart and Amazon are leading an online sales bonanza that will see Indians buy smartphones worth over $1 billion in just five days, according to tech consultancy Counterpoint Research.

Bangalore-based Flipkart said it sold 1 million devices during the first hour of an online phone sale on Thursday that was part of its "Big Billion Days" shopping festival. By the end of the day, it had sold more than 3 million phones.

Acquired earlier this year by Walmart ( WMT ), Flipkart estimated that its sale accounted for more than 85% of all smartphones sold in India on Thursday.

Amazon ( AMZN ) also reported blockbuster device sales during its "Great Indian Festival" sale on Wednesday, cashing in on the big Chinese brands that dominate the Indian market.

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