The Iranian government is seeking information on why Indonesia has detained one of its VLCCs following allegations of an illegal oil transfer.

National Iranian Tanker Co (NITC)'s 317,400-dwt Horse (built 2008) and the Chinese-operated 306,000-dwt Freya (built 2000) were seized by the Indonesia coast guard.

Photographs released by Indonesia show them side by side off Kalimantan province on Sunday.

Iran said the Horse was detained over a "technical issue" and has asked Indonesia to explain the seizure.