Iran, which was India's second biggest supplier of crude oil after Saudi Arabia till 2010-11, sold 759,700 barrels of oil per day to India in October, 56 per cent more than a year ago.
This was larger than 717,000 bpd of oil sold by Saudi Arabia, traditionally India's biggest oil supplier, industry data showed.
Iraq supplied 488,000 bpd.
As western nations imposed sanctions against Iran, the Islamic nation had been relegated to seventh place in 2013-14 and 2014-15 out of the 50-odd nations India sources its crude oil from.
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Saudi Arabia has been India's top supplier of crude oil - selling 35 MT of oil in 2014-15 and 40.04 MT in 2015-16.
However, for the year as a whole Saudi Arabia continues to be the top supplier with 830,000 bpd of oil followed by Iraq at second spot with 784,000 bpd. Iran averaged 456,400 bpd.
Iran had supplied 10.95 million tons of oil to India in 2014-15 fiscal, almost the same as 11 million tons it sold in 2013-14.
The Persian Gulf nation had in 2009-10 supplied 21.2 million tons to India, which came down to 18.5 million tons in 2010-11 and 18.1 million tons in the year after.
After the west imposed sanctions, India brought down the purchases to 13.14 million tons in 2012-13 and had limited them in the years thereafter.