Essar Oil, Iran's leading Indian client, imported 24.6% more oil from Tehran in May compared to a year earlier, according to tanker arrival data obtained from sources and assessed by Thomson Reuters Oil Analytics.
Essar shipped in about 135,800 bpd from Iran in January-May 2015, a decline of about 26.8% from a year earlier, the data showed.
India's imports of Iranian crude rose last month to their highest level since March 2014.
The South Asian nation took about 368,000 bpd Iranian oil last month, a growth of about two-third from a year earlier.
Essar's total crude imports in May rose 6.3% compared with the previous month, the data showed.
India is Iran's second-biggest buyer of oil annually after China.
