Israeli missiles have hit a site in Iran, ABC News reported late on Thursday (April 18), citing a U.S. official, while Iranian state media reported an explosion in the center of the country, days after Iran launched a retaliatory drone strike on Israel.

Reuters could not immediately confirm the reports.

Iran's Fars news agency said an explosion was heard at an airport in the central city of Isfahan but the cause was not immediately known. Iran suspended flights over the cities of Isfahan, Shiraz and Tehran, state media reported.

Several Iranian nuclear sites are located in Isfahan province, including Natanz, centerpiece of Iran’s uranium enrichment program.

Tehran's Imam Khomeini International Airport was closed to all flights until 0700 GMT, according to a notice to airmen posted on a U.S. Federal Aviation Administration database.

Some Emirates and Flydubai flights that were flying over Iran early on Friday (April 19) made sudden sharp turns away from the airspace, according to flight paths shown on tracking website Flightradar24.