It bought one Very Large Crude Carrier (VLCC), or 2 million barrels, of Nigerian Bonny Light and Bonga grades from oil major Shell and 1 million barrels of Azerbajan's Azeri Light.
Price details have yet to emerge.
IOC issued three tenders in March, buying mostly West African crude as improving refining margins and a tightening of supply raised demand for Nigerian and Angolan grades.
IOC bought 950,000 barrels of Bonny Light
In its second tender of the month, it bought 1 VLCC of West African crude oil made up of a cargo each of Qua Iboe
In its first March tender, IOC took 4 million barrels of Nigerian crude.