Iran's navy has begun manoeuvres in the area of the Strait of Hormuz, where one-fifth of the world's oil passes.
State TV said the manoeuvres began early today, involving warships, submarines jet fighters and hovercrafts.
The drills come as the West increases its pressure over Iran's nuclear programme.
The West suspects it may be aimed at producing nuclear weapons, a charge Iran denies.
Iran has threatened to close the straits over Western sanctions but has not repeated the threats lately.
The report said Iran warned ships to stay away from the site until January 3.
The manoeuvres cover nearly 400,000 square miles from the Strait of Hormuz to a northern part of the Indian Ocean, including the Sea of Oman.Reuse content