“I will say that the Iranian state media has not been a very good scribe about what’s happened in the conflict thus far. So I’m extremely sceptical of this,” Vance told a White House briefing.
“I know that we’re investigating.”
Iran has launched fresh attacks on US bases in Kuwait and the United Arab Emirates in response to the alleged strike.
The IRCS said 67 people were hurt when shrapnel from the missile hit a family wedding ceremony, killing at least four people. Iranian state media said a fifth person, a woman aged 22, had died in hospital shortly after.
The four people killed were named locally as Zarkhatoon Taheri, 50; Kolsum Mallahi Nazhdnia, 43; Mohammad Mallahi, 16; and Amirali Karimi, four.
