"The defense ministry announced that the latest version of the Shahab-3 was tested today," IRNA said.
"This experiment on the ground was aimed at evaluating modifications that were recently made to the missile on the basis of research results," the news agency said.
The missile is considered the mainstay of Iran's military technology and portrayed as purely defensive and dissuasive, but specifically as a weapon against Israel.
In the July 28 test of Israel's Arrow II missile, the Jewish state made it clear the improved anti-missile system was aimed squarely at fending off any attack by arch-foe Iran.
Iranian Defense Minister Ali Shamkhani had said Saturday that the test of the Shahab-3 was imminent, adding that the improvements to the missile "not only concern its range, but other specifications as well".
Tehran fears Israel could strike its controversial nuclear program, which Washington suspects is being used to covertly develop weapons.
"The Israelis are trying hard to improve the capacity of their missiles, and we are also trying to improve the Shahab-3 in a short time," Shamkhani said, denying the Islamic republic was working on a more advanced Shahab-4.
Tehran finalised its testing of the Shahab-3 only in June.
The missile, whose name means "meteor" or "shooting star" in Farsi, is thought to be capable of carrying a 1,000-kilogramme (one-tonne) warhead at least 1,300 kilometers (800 miles), well within range of Israel.
Six Shahab-3 missiles were paraded in Tehran in September during commemorations of the 1980-1988 Iran-Iraq war. One of them carried a banner declaring: "We will wipe Israel from the map."
The Shahab-3 is believed to be derived from technology acquired from Pakistan and North Korea, though Shamkhani denied any dealings with Pyongyang.
"If Israel loses its head and attacks Iranian interests, we will deliver a sledgehammer blow to break its bones," Iran's Revolutionary Guards chief General Rahim Safavi said Wednesday, quoted by the student news agency ISNA.
He did not refer specifically to the Shahab.
And President Mohammad Khatami told reporters: "I don't think they (Israelis) would do anything so stupid. That would be very complicated and cost them very dear."
Renewing Iran's denial of seeking nuclear weapons, the pro-reform Khatami said atomic arms were un-Islamic. "Even if they were used against us, we would not use them," he said.