Iran already had reported improvements in a previous missile that would give it the same range as the Ashoura, and Najjar did not elaborate on whether there are any differences between the two weapons.
Recent weapons development has been motivated by Iran's standoff with the United States over its controversial nuclear program, which Washington says is a cover for developing an atomic bomb. Tehran denies that, saying the program is intended to produce electricity.
Iran is known to possess a medium-range missile known as the Shahab-3, which means "shooting star" in Farsi, with a range of at least 800 miles. In 2005, Iranian officials said they had improved its range to 1,200 miles, equal to the new missile announced yesterday.
Analysts also believe Iran is developing the Shahab-4 missile, thought to have a range of 1,200 to 1,900 miles that would enable it to hit much of Europe.
In Israel, there was no official reaction to Iran's statement. But missile specialist Uzi Rubin, formerly head of the Arrow antimissile project in Israel's Ministry of Defense, said the announcement had long been expected.
Rubin said Israel already was in range of other Iranian missiles, so "the people who need to be really worried about the new missile are in Europe."
Meanwhile, a former Iranian nuclear negotiator was acquitted yesterday of spying charges but convicted of acting against the Islamic government in a case that has become a centerpiece in the feud between hard-line President Mahmoud Ahmadinejad and his top political rival.
The verdict for Hossein Mousavian appeared to be a setback for Ahmadinejad, who had branded the diplomat a "spy" and made a veiled reference to him and other critics of his nuclear policies as "traitors."
Mousavian is a close ally of former president Hashemi Rafsanjani, a powerful figure in Iran's clerical leadership who is seen as a pragmatist. Allies of Rafsanjani have been increasingly public in their criticism of Ahmadinejad, accusing him of mismanaging the nuclear standoff with the West and of lashing out against his rivals.