The move by BPCL indicates that refiners will try to frontload their purchases from Iran ahead of a November US deadline for re-imposing sanctions on the country's oil sector, Reuters reported.
Uncertainties cloud Iran's oil exports after US President Donald Trump abandoned a 2015 nuclear agreement last month and ordered the re-imposition of US sanctions on Tehran.
"At this point of time Iranian crude is attractive ... it is faring better than spot cargoes and other crudes," said one of the sources.
Iran has agreed to provide almost free shipping to Indian refiners in 2018-19, an incentive that significantly reduces the landed cost of Iranian oil compared to rival regional grades.
India is Iran's top oil client after China and was one of the few nations that continued to trade with Tehran during the previous round of Western sanctions as New Delhi follows only the restrictions imposed by United Nations.
An Indian delegation with officials from the finance, petroleum and foreign ministries will visit European nations for a week from Monday to explore ways to continue to trade with Iran despite U.S. sanctions, a government official said.
European states have been scrambling to save the 2015 nuclear deal and planning a package of economic relief to persuade Iran to stay in the deal.
"Europe has taken a position, which is different this time. This time we are in the same boat," this official said.
The Indian delegation will visit France, Germany, Britain and Brussels to meet government officials and bankers.