Iran's Revolutionary Guards said Monday an oil tanker caught fire in the Strait of Hormuz after hitting a mine, the latest such incident since Tehran tightened its grip of the waterway.

Iran seized control of the strait after war broke out against the United States and Israel late February, choking off the vital shipping route which normally carries about a fifth of the world's oil.

The Islamic republic has demanded that all ships seek its authorisation before transiting.

"An oil tanker, which was in violation, struck a naval mine south of the Strait of Hormuz, resulting in an explosion and a fire in its engine room," Iranian state media quoted the Guards as saying.

The tanker was travelling in the strait's "unauthorized southern route" and had disabled its positioning and navigation systems, the statement said.

It came a day after the Guards said two oil tankers caught fire in the strait, both after hitting mines.

The Guards' naval commander Admiral Ali Ozmaei warned this week that any vessel that deactivated its navigation systems would be considered "hostile".

The United States has imposed a naval counter-blockade on Iranian oil exports in response to Tehran's blockade on the waterway.