Iranian state media report the military has successfully test fired its longest-range missile. The test is part of military exercises that coincide with new accusations from the U.S. and others about Tehran's nuclear ambitions.
The Shahab-3 missile is thought to have a range of some 2000 kilometers, enough to put Israel, most Arab states and southern Europe in its sights.
State TV broadcast the countdown and launch.
Tehran, which introduced the missile last year, says it is meant to act as an interceptor to deter any foreign attack.
But some western defense analysts believe the Shahab-3 is capable of carrying a nuclear warhead. Earlier this year, Tehran's arch-enemy Israel test fired its own Arrow 2 missile in a simulation of stopping the Shahab-3.
Iran's military exercises, which started Sunday and have included test launches of short- and medium-range missiles as well, come just days after the disclosure that Tehran is building a new uranium enrichment plant.
Iran was apparently forced to reveal its existence after it became aware that western intelligence agencies had known about it for years.
Tehran denies there was any secrecy involved, and that the plant hadn't reached the point where the government needed to disclose its existence.
Major world powers disagree and are expected to drive that point home with the threat of further sanctions in talks with Iranian nuclear representatives in Geneva Thursday.
Iran argues that it has a right to nuclear energy, a point of agreement with Western powers. But the West and the U.N.'s International Atomic Energy Agency want greater access to Iran's nuclear facilities to ensure that energy is all that Tehran is seeking.