Iran is said to have up to six Russian built SSK or SSI Kilo-class diesel submarines. Iran has focused their attention on miniature submarines designed to protect, defend, or disrupt shipments in the Strait of Hormuz. According to Iranian officials, the miniature sub is hard to detect given it size, speed and the dept of the Persian Gulf. How many of these in Iran's inventory is unknown, but all sources can agree that Iran has managed to build more than one of these miniature submarines.
More than likely these would be used against oil tankers to disrupt the flow of oil in the Persian Gulf.