Commercial flights began diverting from their routes over western Iran early Friday morning without explanation as one semiofficial news agency in the Islamic Republic claimed there had been “explosions” heard over the city of Isfahan, while state television acknowledged “loud noise.”

The move comes as tensions remain high in the wider Middle East after Iran’s missile-and-drone attack on Israel last weekend — an event that was itself retaliation against a suspected Israeli strike in Syria on April 1, which claimed the lives of several senior Iranian military commanders.

ABC News is reporting that Israeli missiles have hit a site in Iran, citing a U.S. official.

Dubai-based carriers Emirates and FlyDubai began diverting flights around western Iran about 4:30 a.m. local time. They offered no explanation, though local warnings to aviators suggested the airspace may have been closed.

The semiofficial Fars news agency reported on the sound of explosions over Isfahan near its international airport. It offered no explanation for the blast.

Iran later announced it grounded commercial flights in Tehran and across areas of its western and central regions. Loudspeakers informed customers of the incident at Imam Khomeini International Airport in Tehran, online videos purported to show.

Isfahan is home to a major airbase for the Iranian military, as well as sites associated with its nuclear program. Iran’s government offered no immediate comment.

Iranian state television began a scrolling, on-screen alert acknowledging a “loud noise” near Isfahan, without immediately elaborating.