Washington denied any knowledge of the blast. The Al-Alam station, broadcasting in Arabic, later dropped the reference to the missile and said a fuel tank might have fallen from a plane.
After oil markets ticked up and the US stock market briefly dropped, Iranian officials quelled concern by announcing the blast was linked to construction of a dam.
Iran's Chief nuclear negotiator, Hassan Rohani, saw a calculated campaign by the United States and the Western media which acted on the Al-Alam report.
"This fuss over an explosion shows that they use any excuse to attract attention towards Iran's nuclear programme," Rohani told state television.
"Reports of a strike were false and are psychological warfare."
The explosion was reported near the town of Dailam 100 miles (160 Km) from the Russian-built Bushehr nuclear plant.
Washington accuses Tehran of pursuing atomic weapons. US Secretary of State Condoleezza Rice has said that a US attack on Iran is not imminent but that the option remains available.
Israel, which like its US ally accuses Iran of trying to build nuclear arms, said on Wednesday Iran was six months away from having the knowledge to build a bomb.
Iran says its nuclear facilities would only be used for peaceful purposes.
In the past, Israel has warned Iran of possible pre-emptive military attacks on its nuclear facilities similar to Iraq's Osiraq reactor in 1981 that caused a blow to Saddam Hussein's nuclear programme.
Economic Analyst Saeed Leylaz said Tehran and Washington may be examining global consequences of a possible US military strike on Iran's nuclear facilities.
"Iran wanted to warn America of economic outcomes of any attack on the country's nuclear facilities," Leylaz told Reuters.
As the blast occurred at a time of heightened tension between Washington and Tehran, the report jolted both the oil market and stock market. "The result showed that a real strike can shake the world."
Intelligence Minister Ali Yunesi said on Wednesday Washington was using satellites to gather evidence of Iran's nuclear programme.
The Washington Post, citing information from unnamed US officials, reported this week that the United States had been flying into Iran looking for evidence of nuclear weapons programs.
The pilotless planes flew into Iran from US military bases in Iraq using radar, photography and air filters to detect traces of nuclear activity, the newspaper said. Iran's Defence Minister Ali Shamkhani said Iran would strongly counter any attack.