There were no details on the torpedo's name, speed and range.
On Sunday, Iran announced a new high-speed torpedo called the Hoot, meaning whale, that the military boasted was too fast for any submarine or warship to elude.
General Mohammad Ebrahim Dehghani told state television the ship-launched weapon could target submarines at any depth and was powerful enough to "break a heavy warship" in two.
Iran said on Monday that its ongoing war games in the Gulf aim to prepare its defences against American threats amid mounting tensions over its nuclear programme.
Known to boast
But the United States said that while Iranians may have made "some strides" in its military, they have also been known to "boast and exaggerate their statements about greater technical and tactical capabilities".
Ali Ansari, an Iran specialist at Britain's Royal Institute for International Affairs, said there was very likely "a little bit of bluster" in Iran's claims about its new weapons.
They aim to "prove to the West that they can hit Israel and close the Straits of Hormuz. They're saying if you hit us, then we can hit back," he said.
Commentators say Iran wanted to put on a show of strength against the United States, which has forces in neighbouring Iraq and Afghanistan and in several Gulf nations.
"Islamic Iran will not hesitate to respond to the aggressor enemy"
Iranian military spokesman
General Alireza Afshar, a military spokesman, told the official Islamic Republic News Agency: "The forces in the manoeuvres will show that Islamic Iran will not hesitate to respond to the aggressor enemy with a swift and smashing answer."
Fearing US attack
Many in Iran worry over the possibility of US military action in the escalating dispute over Iran's nuclear ambition, an option Washington has refused to rule out.
Yuryi Baluyevskyi, chief of staff of the Russian armed forces, told Aljazeera that using the military option against Iran would be "another mistake to be added to a series of US mistakes".
The Untied States is pushing for UN sanctions against Iran, accusing it of seeking to develop nuclear weapons.
Tehran denies the claim, saying its programme aims to generate electricity.
It has so far rejected a demand by the UN Security Council that it give up uranium enrichment, a key part of the nuclear process that can produce either fuel for a reactor or material for a warhead.
Iran's military has been working to boost its domestic production of armaments.
Since 1992, Iran has produced its own tanks, armoured personnel carriers, missiles and a fighter plane. It announced in early 2005 that it had begun production of torpedoes.
Iran bought three Russian Kilo-class submarines in the 1980s and has since said it is producing its own smaller-sized subs, at least two of which are believed to have been built and entered into the country's fleet.