Iranian state television reported on Thursday: "Dozens of missiles were fired including Shahab-2 and Shahab-3 missiles. The missiles had ranges from 300km up to 2,000km."
The television station said that the military manoeuvres, named Great Prophet Two, would last until November 11 and include drills in the gulf and Sea of Oman, and would be a show of defensive strength.
General Yahya Rahim Safavi, commander of the Revolutionary Guards, was quoted as saying: "The war games are aimed at demonstrating the deterrent power of the [Iranian Revolutionary] guards against possible threats."
Safavi said the drills were not a threat to Iran's neighbours.
"Our neighbours are our friends," he said. "The guards just want to prove that they ready to resist in any threatening situation."
Iranian television footage of the missile launches showed the rockets leaving long vapour trails as they soared into the air above the desert near the holy city of Qom in central Iran.
As they rose into the sky, Safavi, who gave the firing order, and other guardsman were heard shouting: "God is the Greatest".
The announcement came two days after US-led warships finished a two days of exercises in the gulf which were described by Iran as "adventurist".
Iran said the drills involving Australia, Bahrain, Britain, France, Italy and the US would not improve security in the waters of the gulf, through which about 20 per cent of the world's oil passes. It also called on gulf nations to set up their own regional security arrangements.
Iran has nuclear-capable missiles which are able to hit Israel
The US-led manoeuvres focused on surveillance, with warships tracking a ship suspected of carrying components of illegal weapons.
The Shahab-3 missile is capable of carrying a nuclear warhead and has a range of more than 2,000km - enough to reach Israel and US forces based in the Middle East.
These are the country's third war games this year.
In August, Iranian armed forces held a cross country military exercise called Zolfaghar Blow to test new weapons and tactics against a potential enemy. The first stage of the Great Prophet war games was held in April.