Tehran denies the men are members of the Revolutionary Guard as tensions between Iran, Saudi Arabia increase
Iran on Wednesday demanded the release of three fishermen detained last week by Saudi Arabia, which claims the men were Iranian Revolutionary Guard members planning an attack.
The interior ministry called in a statement for "the release as quickly as possible of the three fishermen" detained in the Gulf by the Saudi coastguard.
Iran has denied the men are members of the Revolutionary Guard and accused the coastguard of killing another fisherman when two Iranian boats strayed into Saudi waters on Saturday.
The ministry called for the "punishment" of those responsible for the killing.
Riyadh said Monday it had captured three Revolutionary Guards members aboard an explosives-laden boat heading to an oil platform in the Gulf and planning to carry out "a terrorist act".
The incident has increased tensions between Riyadh and Tehran, arch-rivals opposed in a wide range of conflicts throughout the Middle East.