Washington, which says Iran seeks atomic bombs, told Tehran to halt further tests if it wanted the world to trust it. Iran, the world's fourth largest oil producer, insists its nuclear programme aims only at generating electricity.
Rising tensions have rattled financial markets. Oil prices, which had slipped from record highs, rebounded about $2 a barrel after today's tests.
Speculation that Israel could strike Iran has mounted since its air force staged an exercise last month that US officials said involved 100 aircraft. The United States has not ruled out military action if diplomacy fails to resolve the nuclear row.
"We warn the enemies who intend to threaten us with military exercises and empty psychological operations that our hand will always be on the trigger and our missiles will always be ready to launch," Revolutionary Guards air force commander Hossein Salami said, according to ISNA news agency.
In televised comments, he said thousands of missiles were ready to be fired at "specific and pre-determined targets". Missiles were shown soaring from desert launchpads, leaving long vapour trails.
Iran should "refrain from further missile tests if they truly seek to gain the trust of the world," White House spokesman Gordon Johndroe said.
US Secretary of State Condoleezza Rice suggested the tests justified an American missile shield plan with bases in eastern Europe that Russia strongly opposes.
"Those who say that there is no Iranian threat against which to be building missile defences perhaps ought to talk to the Iranians about ... the range of the missiles that they test fired," Rice said in Bulgaria.
Russia, which has resisted US calls for tougher UN sanctions on Iran, nevertheless says it shares concerns about Tehran's nuclear programme. It responded to an Iranian rocket test in February by questioning Tehran's motives.
Italy joined criticism of Iran's latest missile tests.
"These are very dangerous missiles - that's why the international community and not just Israel has an interest in blocking this escalation in a definitive way," Italian Foreign Minister Franco Frattini said in Ramallah, in the West Bank.
Iran's State Press TV said the "highly advanced" missiles tested by the Guards included a "new" Shahab 3 missile, which officials have said could reach targets 1,250 miles away. Iran has said Israel and US bases are in its range.
Some US facilities across the Gulf are little more than 200 km from Iran's coast, putting them well within range of Iranian missiles, even if analysts question their accuracy.
The United States also has forces based in nearby Arab states, including Qatar and Bahrain, along with ships patrolling the Gulf waterway.
Iran has said US forces are vulnerable because of their presence in two of its neighbours, Iraq and Afghanistan.
Israel, believed to be the Middle East's only nuclear-armed power, has vowed to prevent Iran from acquiring an atomic bomb.
"Israel does not threaten Iran, but the Iranian nuclear programme, combined with their aggressive ballistic missile programme, is a matter of grave concern," Mark Regev, spokesman for Israeli Prime Minister Ehud Olmert, said after the tests.
Leaders of the Group of Eight rich countries voiced serious concern yesterday at the proliferation risks posed by Iran's nuclear work. World powers have offered Iran incentives if it will suspend uranium enrichment. Tehran has rejected the demand.
Iran has threatened to close the Strait of Hormuz, conduit for about 40 per cent of globally traded oil, if it is attacked. The US military says it will prevent any such action.
An aide to Iran's Supreme Leader was quoted as saying yesterday that his country would hit Tel Aviv, US shipping in the Gulf and US interests in reply to any military strike.
© Thomson Reuters 2008